"Fulldeckisms" are short insults or ways to say someone is dumb, named after the classic "a few cards/ace/kings/etc short of a full deck".  This list is taken from one commonly posted to various newsgroups such as alt.quotations, with a few of my own and a few submitted ones added in. Submit your additions here.

Last updated November 7, 2002.

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• Body by Fisher -- brains by Mattel."
• $HOME = /dev/null.
• 3K RAM free, no EMS.
• A 10K brain attached to a 9600 baud mouth.
• A 3.5-inch drive, but data on punch cards.
• A brain like a BB in a boxcar.
• A couplet short of a sonnet.
• A day late and a dollar short.
• A deadbolt with a broken cylinder.
• A few beers short of a six-pack/a six-pack short of case.
• A few bombs/melons short of a full load.
• A few bricks short of a wall/hod.
• A few clowns short of a circus.
• A few French fries short of a Happy Meal.
• A few open splices.
• A few peas short of a casserole.
• A few pickles short of a jar.
• A few pies short of a holiday.
• A few planes short of an Air Force.
• A few revisions behind.
• A few sandwiches short of a picnic.
• A few screws loose.
• A few spoons short of a full set.
• A few tiles missing from his space shuttle.
• A few tiles short of a successful re-entry.
• A few too many lights out in his Christmas tree.
• A few volts below threshold.
• A few yards short of the hole.
• A flower short of an arrangement.
• A flying buttress short of a cathedral.
• A handle short of a suitcase.
• A kangaroo loose in her top paddock.
• A lap behind the field.
• A little light in his loafers.
• A looney tune.
• A mental midget. -- Moe Howard (?)
• A modest little person, with much to be modest about. -- Churchill
• A Neanderthal brain in a Cro-Magnon body.
• A notch off the timing mark.
• A one-bit brain with a parity error. 
• A pane short of a window.
• A photographic memory, but the lens cover is glued on.
• A quart low.
• A return with no gosub.
• A room temperature IQ.
• A semitone flat on the high notes.
• A signature short of a book.
• A sleeve/button short of a shirt.
• A span short of a bridge.
• A square with only three sides.
• A teabag short of a pot.
• A teapot with a cracked lid.
• A titanic intellect... In a world full of icebergs.
• A tower short of a castle.
• A vacuum-tube brain in a microchip world.
• A VGA card and a Herc monitor.
• A victim of retroactive birth control.
• A violin minus the bow.
• A wind-up clock without a key.
• Airhead / bubble-brain.
• All booster, no payload.
• All crown, no filling.
• All hammer, no nail.
• All hat and no cattle.
• All his eggs in the same basket.
• All missile, no warhead.
• All shot, no powder.
• All the lights don't shine in her marquis.
• All the personality of linoleum flooring / plasticene / putty / caulking / saran wrap.
• All the sex appeal of a wet paper bag.
• All wax and no wick.
• Always in the right place, but at the wrong time.
• Always sharpening his sleeping skills.
• An 8080 in a 68000 environment.
• An Apple //e on UUCP.
• An ego like a black hole.
• An experiment in Artificial Stupidity.
• An expert on the historical significance of cottage cheese.
• An intellect rivaled only by garden tools.
• An XT clone in a Pentium zone.
• Ano-fossal ambiguity (can't tell his ass from a hole in the ground).
• Any slower and he'd be in reverse. -- Gignac
• As bright as a nightlight / small appliance bulb / tulip bulb.
• As happy as if he had brains.
• As quick as a corpse.
• As sharp as a marble / bowling ball / beachball / pin head / bowl of Jello, and twice as smart.
• As sharp as a sack full of wet mush. -- Foghorn Leghorn
• As smart as a politician/lawyer is honest.
• As smart as bait.
• As smart as Christie Brinkley is ugly.
• As thick as two short planks.
• Attic's a little dusty.
• Back burners not fully operating.
• Bad spot on the disk.
• Bats in the belfry.
• Batteries not included.
• Been napping in front of the ion shield again.
• Been playing with his wand too much.
• Been playing with the pharmacy section again.
• Been short on oxygen one time too many.
• Been using her head as a mass driver.
• Better at sex than anyone; now all he needs is a
• partner.
• Blew his O-rings.
• Blew the hatch before the lock sealed.
• Blocked one too many hockey pucks / soccer balls / punches with his head.
• Born a day late and like that ever since.
• Born ugly and built to last.
• Both oars in the water, but on the same side of the boat.
• Bright as Alaska in December.
• Bright as an acetylene torch -- without an oxygen supply.
• Bubbles in her think tank.
• Caboose seems to be pulling the engine.
• Calling her stupid would be an insult to stupid people.
• Calling him a pea brain would be an undeserved compliment.
• Can be outwitted by a jar of Marshmallow Fluff.
• Can't find his ass with two hands and a periscope/ compass/flashlight/bloodhound (in a locked closet).
• Car's only got three wheels, and one's going flat.
• Carries a tire gauge in her purse.
• Cauliflower for brains.
• Charming as a carbuncle.
• Cheezwiz for brains.
• Chimney's clogged.
• Clock doesn't have all its numbers.
• Collects cards for Craig.
• Consumes hard drugs as vitamins.
• Contributes to the population problem.
• Couldn't organize a piss-up in a brewery. (Common in Australia.)
• Couldn't pour water out of a boot with instructions on the heel.
• Couldn't think his way out of a paper bag.
• CPU not connected to the bus.
• Cranial cavity filled with neutronic matter. (Really dense.)
• Cranio-rectally inverted.
• Cursor's flashing but there's no response.
• Depriving some village of an idiot.
• Defective hard drive / boot sector.
• Diarrhea of the mouth; constipation of the ideas.
• Does aerobics... in his head.
• Does everything the hard way, like making love standing up in a hammock.
• Doesn't have all his cornflakes in one box.
• Doesn't have all his dogs on one leash / cups in the cupboard / groceries in the same bag.
• Doesn't have all the dots on his dice / pens in her plotter.
• Doesn't have both oars in the water.
• Doesn't have his belt through all the loops.
• Doesn't have the sense God gave an animal cracker.
• Doesn't have two neurons to rub together.
• Doesn't just know nothing; doesn't even suspect much.
• Doesn't know much, but leads the league in nostril hair. -- Billing
• Doesn't know which side the toast is buttered on.
• Doesn't quite sample at the Nyquist rate.
• Donated her body to science... before she was done using it.
• Downhill skiing in Iowa.
• Driving with two wheels in the sand.
• Dropped his second stage too soon.
• Dumb as asphalt / a stump / a sack of hammers.
• Dumber than a chicken / box of hair/rocks.
• Easier to count the bricks left than the bricks missing.
• Echoes between the ears.
• Eight pawns short of a gambit.
• Elevator doesn't go all the way to the top floor / penthouse.
• Elevator goes all the way to the top but the door doesn't open.
• End of season sale at the cerebral department. -- Gareth Blackstock
• Fighting the war with a starter pistol / water pistol / pop gun / cap gun.
• Finds a flat by swapping tires.
• Finds canonical humor collections amusing.
• Fired from McDonald's for having a short attention span.
• Fired her retro-rockets a little late.
• Flaky.
• Flying/landing on one engine.
• Folds ace plus red jack hand when playing blackjack.
• Forgot to pay his brain bill.
• Four cents short of a nickel.
• Fruity as a nutcake.
• Full throttle, dry tank.
• Gasoline engine, diesel fuel.
• Gates are down, the lights are flashing, but the train isn't coming.
• Gavel doesn't quite hit the bench.
• Gets hypnotized on the despun section.
• Goalie for the dart team.
• Got a life, but wasn't sure what to do with it.
• Guillotining him would make only an aesthetic difference.
• Gyros are loose.
• Had a head crash.
• Half a bubble off plumb. -- attributed to Mark Twain
• Hard to tell if he has an ace up his sleeve or if the ace is missing from his deck altogether.
• Has a few wait states.
• Has a full six-pack but lacks the plastic thing to hold them together.
• Has a leak in his ceiling.
• Has a one-way ticket on the Disoriented Express.
• Has a slow clock.
• Has all her bricks, but no cement holding them together.
• Has all the brains God gave a duck's ass.
• Has an IQ of 2, and it takes 3 to grunt.
• Has his solar panels aimed at the moon.
• Has it floored in neutral.
• Has no discretionary intellect.
• Has no upper stage.
• Has signs on both ears saying "Space for Rent".
• Has so few thoughts that when he free associates, it's like watching tennis.
• Has the attention span of an overripe grapefruit.
• Has the brains of a house plant.
• Has the Grand Canyon under the crew cut.
• Has the IQ of a salad bar / ice cube.
• Has the mental agility of a soap dish.
• Has two brains; one is lost and the other is out looking for it.
• Hasn't got all his china in the cupboard.
• Hasn't got the brains God gave a cat.
• Having a party in his head, but no one else is invited.
• He fell out of the ugly tree and hit every branch on the way down.
• He's diagnosable.
• He's not stupid; he's possessed by a retarded ghost.
• He's so dense, light bends around him.
• Her ass is sucking swamp gas.
• Her brain is more like a Rube Goldberg device than a computer.
• Her dentist went deaf from the drill's echoes.
• Her dialing thumb must be broken.
• Her memory is truly random-access.
• Her mere presence causes parity errors, power fails, and head crashes.
• Her modem lights are on but there's no carrier.
• Her phone doesn't quite reach her desk.
• Her sewing machine's been out of thread for some time now.
• Her synapses are about |that| far apart.
• Her tires are a little low.
• Hid behind the door when they passed out brains.
• His antenna doesn't pick up all the channels.
• His buffer is full.
• His elevator is stuck between floors.
• His family wasn't dysfunctional until he arrived.
• His head whistles in a cross wind.
• His mind is on vacation but his mouth is working overtime.
• His picture is in the dictionary under "zero".
• His puzzle is missing a few pieces.
• His seat back is not in the full upright and locked position.
• His signal-to-noise ratio is epsilon.
• His system administrator is never in.
• I'd like to buy him for what he's worth and sell him  or what he thinks he's worth.
• If brains were bird droppings, he'd have a clean cage.
• If brains were dynamite, she wouldn't have enough to
• blow her nose / the wax out of her ears.
• If brains were gasoline, he wouldn't have enough to drive a dinky car around the inside of a cheerio.
• If brains were lard, he'd be hard pressed to grease a small pan.
• If brains were taxed, he'd get a rebate.
• If brains were water, hers wouldn't be enough to baptize a flea.
• If he gets any denser, the geocentric theory of the universe will come true.
• If he had another brain, it would be lonely.
• If he had brains, he'd take them out and play with them.
• If he had half a brain, his ass would be lopsided.
• If he were any more stupid, he'd have to be watered twice a week.
• If her brains were put in a hummingbird, it would fly backwards.
• If his IQ was two points higher he'd be a rock.
• If she was any dumber, she'd be a green plant.
• If they knock heads, implosion will suck all the air out of the room.
• If what you don't know can't hurt you, she's practically invulnerable.
• If you give him a penny for his thoughts, you get change back.
• If you stand close enough to him, you can hear the ocean.
• In need of a ROM upgrade.
• In the shopping mall of the mind, he's in the toy store.
• Infinite space between her ears.
• Informationally deprived.
• Inspected by #13.
• Intellectually challenged.
• IQ = dx / (1 + dx), where x = age.
• Isn't carrying a full set of golf clubs.
• It's hard to believe he beat 100,000 other sperm.
• Just another flash in the bedpan.
• Knitting with only one needle.
• Leaky sunroof.
• Left hand threaded.
• Left his booster on the launch pad.
• Left the store without all of his groceries.
• Life by Norman Rockwell, but screenplay by Stephen King.
• Lights are on but nobody's home.
• Lights not burning too bright.
• Like a loose-leaf folder in winter.
• Likes dunking for french fries.
• Little red choo-choo's gone chugging 'round the bend /
• jumped the track.
• Lives in La-la-land.
• Living proof that nature does not abhor a vacuum.
• Long on dry wall, short on studs.
• Loose chip on the microprocessor board.
• Loose wire to his headset/ringer.
• Low on thinking gas.
• Lugnuts rattling in the hubcaps.
• Made a career out of mid-life crisis.
• Mainspring's wound too tight.
• Mentally qualified for handicapped parking.
• Metronome needs oil.
• Mind like a steel sieve.
• Mind like a steel trap -- everything gets mangled / full of mice / nothing in, nothing out / rusted shut.
• Missing a few buttons on his remote control.
• Missing a few catalog cards / gears / marbles.
• Missing a layer of insulation in his attic.
• Mouth is in gear, brain is in neutral.
• Needs another brain to make half-wit.
• Needs both hands to wipe his behind.
• Needs his sleeves lengthened by a couple of feet so they can be tied in the back.
• Never had a headcold in her life since diseases can't exist in a vacuum.
• Nice house but not much furniture / nobody lives there.
• Nine pence in the shilling.
• Nineteen cents short of a paradigm.
• No filter in the coffeemaker.
• No grain in the silo.
• No hay in the loft.
• No one at the throttle.
• No wind in her mind's windmills.
• Not digging in the same ditch with the rest of us.
• Not enough brains cells for the Prozac to be effective.
• Not enough brains to get anywhere *near* the gutter.
• Not enough change to break a dollar.
• Not enough sense to come in out of the rain.
• Not enough sense to stay out in the rain (like a 60's flower child).
• Not firing on all four/six/eight cylinders.
• Not hard-docked.
• Not inflated to 90 PSI.
• Not playing with / dealing from a full deck (-- not even in the game).
• Not the pointiest quill on the porcupine.
• Not running on full thrusters.
• Not the brightest bulb on the Christmas tree.
• Not the full quid.
• Not the same since they took him off his medication.
• Not the sharpest knife in the drawer.
• Not the shiniest penny in the fountain.
• Not worth pissin' on.
• Not wrapped too tight.
• Nothing between the stethoscopes.
• Number 'n a hake. (New England expression a notoriously stupid fish.)
• Nutty as a fruitcake.
• Off his rocker.
• Oil doesn't reach his dipstick.
• On the batting end of a no-hitter.
• One bit short of a byte.
• One board short of a porch.
• One boot stuck in the sand.
• One bun/donut short of a dozen.
• One card/marble shy of a full deck.
• One drop short of an empty bladder.
• One Froot Loop shy of a full bowl.
• One hot pepper short of an enchilada.
• One live brain cell away from being a talking monkey.
• One of the early failures of electroshock therapy.
• One sentence short of a paragraph.
• One shade short of a rainbow.
• One shingle shy of a roof.
• One ship short of a full fleet.
• One side short of a pentagon.
• One snowflake short of a ski slope.
• One step short of the attic.
• One taco short of a combination plate.
• One tree short of a hammock.
• One weight short of a shipwreck.
• Only one oar in the water.
• Only playing with 51 cards.
• Only playing with the jokers.
• Operating in stand-by mode.
• Ought to have a warning label on his forehead.
• Out there where the buses don't run.
• Over the rainbow.
• Overruns above 110 baud.
• Paged/swapped out.
• Paralyzed from the neck up.
• Parked his head and forgot where he left it.
• Pedaling real fast, but not getting anywhere.
• Permanently out to lunch.
• Permanently rotated 90 degrees from the rest of us.
• Pins 2 and 3 (RS-232) permanently connected to ground.
• Playing an endgame with a king and no other pieces.
• Playing baseball with a rubber bat.
• Playing hockey with a warped puck.
• Playing Scrabble, but we can't figure out what words he's building.
• Plays pinochle with a poker deck.
• Plays solitaire... for cash.
• Plays tennis with no net and finds it challenging.
• Posts empty articles to Usenet, and enjoys rereading them later.
• Pressure's up, but there's a slow leak somewhere.
• Proof that evolution *can* go in reverse.
• Put a lens in each ear and you've got a telescope.
• Puts a finger in his ear so the draft through his head isn't annoying.
• Putting his brain on the edge of a razor blade would be like putting a pea on a six lane highway.
• Racing fifty yards with a pregnant woman, he'd come in third.
• Reading from an empty/blank/unformatted disk.
• Reads Homer in the original Greek, but doesn't know Greek.
• Ready to check in at the HaHa Hilton.
• Ready to join the Anti-Mensa Society.
• Receiver is off the hook.
• Relatively three-dimensional, as fictional characters go.
• Renewable energy source for hot air balloons.
• Reset line is glitching.
• Result of a first cousin marriage.
• Room for rent, unfurnished.
• RS232C brain with a DIN connector.
• Running at 300 baud.
• Running on empty.
• Running U.S. appliances on British current.
• Runs squares around the competition.
• Rusty springs in the mousetrap.
• S p a c e d o u t .
• Sailboat fuel for brains.
• Sat under the ozone hole too long.
• Sending back packets, but the checksums are wrong.
• Seven seconds behind, and built to stay that way.
• Several nuts short of a full pouch.
• She wears a pony tail to cover up the valve stem.
• Short a few cards.
• Short-circuited between the earphones.
• Should have kept his helmet on while riding / playing.
• Single-sided, low density.
• Skating on the wrong side of the ice.
• Skylight leaks a little.
• Slept too close to his radium-dial watch.
• Slinky's kinked.
• Sloppy as a soup sandwich.
• Slow as molasses in January.
• Smoke doesn't make it to the top of his chimney.
• So dim that his psychic carries a flashlight.
• So fat that people jump over him rather than go around.
• So slow he has to speed up to stop.
• So stupid, mind readers charge her half price.
• Solid concrete from the eyebrows backwards.
• Some bugs in his software.
• Some drink from the fountain of knowledge, but he just gargled.
• Some pages missing.
• Someone blew out his pilot light.
• Someone else is doing the driving for that boy.
• Someone let the air out of her lock.
• Someone pissed in his gene pool.
• Sort of like an inverse Einstein.
• Source code is missing a few lines.
• Stocksy-babes (a truly vile British-slang insult).
• Strong like bull, smart like streetcar.
• Subtle as a well-thrown brick.
• Suffers from Clue Deficit Disorder.
• Surfing in Nebraska.
• Swimming in the shallow end of the gene pool.
• Switch is on, but no one's receiving.
• Teflon brain -- nothing sticks.
• The best part of him ran down his mother's legs. -- Jackie Gleason
• The cheese slid off his cracker.
• The fan is working but the freon's leaked out.
• The going got weird, and he turned pro.
• The heater's plugged in but the rheostat's shot.
• The spit valve's fallen off his trumpet again.
• The twinkle in his eyes is actually the sun shining between his ears.
• The wheel's spinning but the hamster's dead.
• There's nothing wrong with you that couldn't be cured with a little Prozac and a polo mallet. -- Woody Allen
• Thick as a brick.
• Thinks at 5 baud.
• Thinks cellular phones are carbon-based life forms.
• Thinks E=MC^2 is a rap star.
• Thinks in lower case and types accordingly
• Thinks like a boar hog looks at a wristwatch.
• Thinks Moby Dick is a kind of venereal disease.
• Three chickens short of a henhouse.
• Too many birds on her antenna.
• Too many jokers and not enough aces in his deck.
• Too much yardage between the goal posts.
• Top paddock is full of rocks.
• Toys in the attic.
• Train of thought derailed / still boarding at the station.
• Traveling faster than light, but left his sneakers behind.
• Trying out for the javelin retrieval team.
• Tuning in shortwave with a TV antenna.
• Two bits shy of a word.
• Two chapters short of a novel.
• Two degrees off square.
• Two inches taller than spherical.
• Two saucers short of a tea-service.
• Two sheep short of a sweater.
• Two socks short of a pair.
• Two suits short of a full deck (a half-wit).
• Ugly as a warthog and half as smart.
• Unclear which of Newton's three laws of motion keeps his ears apart.
• Useful as a hip pocket on a T-shirt.
• Useful as an ashtray on a motorcycle.
• Useful as tits on a bull / boar-hog.
• Uses his head to keep the rain out of his neck.
• Using a 1S-2D floppy for brains in a world of hard disks.
• Vacancy on the top floor.
• Vertically-fornicated mind.
• Was born an acrobat but landed on his head.
• Was first in line for brains, but ended up holding the door open.
• Was left on the Tilt-A-Whirl a bit too long as a baby.
• Was napping in the nut pile the day God was cracking nuts.
• Wasn't abused as a child, but should have been.
• Wasn't strapped in during launch.
• Watches "Beavis and Butthead" to learn vocabulary.
• Went in for repairs but wasn't tightened with a torque wrench.
• With one more neuron he'd have a synapse.
• Would make an excellent illustration in a proctolgy textbook.
• Zero K memory.

Suggest additional terms to add here.  But only if they're funny.