I've been compiling a list of funny MAME games to add as a genre to Hyperspin. I've been hunting around the Internet and using my own experience, but I bet there are a lot that I've missed.
Help me out! I'm looking for games that are funny for adults, but I'm keeping this list pretty much SFW, so no porn games, please. 
Here's what I have so far:
Anteater - a maze game where you extend an anteater's tongue deep underground
Arch Rivals - basketball precursor to NBA Jam with punching and pantsing. 
Arm Wrestling  the lesser known dual screen twin of Nintendos Punch out
B. Rap Boys  super wacky beat em up full of 90s tude
Bad Dudes versus Dragon Ninja  data East classic for the ages
Bank Panic  three doors, three buttons
Battle Circuit  Capcom sets new standards for strangeness in a beat em up
Blazing Star  a Neo Geo classic with amazing Engrish and a space baby as a final boss
Bonk's Adventure/B.C. Kid - get angry and bash everything with your huge noggin in this special arcade edition that features an extensive level select and 2 player co-op 
Boogie Wings  excellent and unique shooter where your plane has a hook that can pick up everything and you can run as fast as you can fly
Butasan  Pigs and Bombers  control a pig among other pigs in a field of bombs and don't get blown up
Cadillacs and Dinosaurs  an excellent beat em up where you can bully dinosaurs
Calorie Kun vs Moguranian  maze game where you eat stuff and can get stuck in the tunnel because you're too fat
Captain Tomaday  you control a flying tomato shooting down vegetables
Caveman Ninja  now known as the first game in the Joe and Mac series
Chicken Shift  eggs, termites, and wooden ramps, what could go wrong?
Cosmo Gang the Video  trippy reimagining of space invaders
Crazy Climber  everybody hates you for not using the stairs
Crazy Climber 2  still crazy after all these years
Diet Family  shooter where you struggle to not get fat
Dino Rex  wonderfully cheesy digitized graphics
Domino Man  the guy from Tapper has a nightmare
Dynamite Dux  surreal beat em up starring the twisted spawn of Woody woodpecker and Daffy duck
Exterminator  you control a disembodied digitized hand killing hordes of vermin with your finger gun
Fancy World-Earth of Crisis  bubble bobble with teenyboppers
Fantastic Journey/Gokujyou Parodius  excellent and intentionally bizarre Gradius parody
Farmers Rebellion  like seven samurai if one farmer had killed everyone
Fire Trap  crazy climbers dream of what he looks like
Ganbare Ginkun  stick figure minigame madness
Go Go Mr. Yamaguchi  was never localized for some reason
Gridlee  abstract suggestive graphics at their finest
Guardians of the Hood  digitized cross-fitters from Chicago live out their fantasies
Gunbarich  like Arkanoid, but weirder and with pinball flippers
Guzzler  maze game where you drink a lot of water and spit it out
Hatris  Tetris with hats
Im Sorry  a game for Japanese businessmen who dont like taxes
Irritating Maze, The  excellent trackball game with zany Japanese flair
Journey  from the Golden age of game design starring the digitized faces of the 80's band
Jump Kids  toddlers run the gamut of emotions in this bubble bobble clone
Last Resort  another classic Neo Geo shooter, but you are rewarded for killing innocent bystanders and get to see actual bodies plummet out of ships you destroy
Marchen Maze  I suppose a game loosely based upon Alice in Wonderland has to be pretty weird
Metro Cross  sci-fi track and field, but bad
Mug Smashers  sometimes a games blandness is its greatest strength
Munch Mobile/Joyful Road  not Herbie goes on a trip
Jue Zhan Tian Huang  insanely shameless transplant of fighting game sprites into a beat em up
Narc  a classic game with over the top violence clearly inspired by Robocop
Night Slashers  gloriously gory beat em up, the Japanese version has red blood and other changes, but the text of the cheesy story is in Japanese
Ninja Baseball Bat Man  a modern classic
Ninja Clowns  yup
Nitro Ball  sporty homage to Smash TV that is a strange mash-up of pinball and run and gun, with extra points being awarded for shooting enemies into holes or pinball drop targets
Outfoxies  twisted James Bond
Pac & Pal  Pac-Man uses harsh language against the ghosts and steals fruit from a child
Parodius Da!  first arcade title in the classic series
Pigskin 621 AD - hybrid rugby/football game that lets you punch and give your team different strategies, like "scatter" or "bad attitude"
PuLiRuLa  just play it
Quiz and Dragons: Capcom Quiz Game  hope youre brushed up on your 20 century trivia
Rock n Rage  control a rockstar raging in another dimension
Screw Loose  imagine Robotron, but all the good ideas are taken
Scud Hammer  a PG version of one of those Japanese beat-up-annoying-people games
Smash TV  this classic aged better than the Running Man movie it spoofs
Snacks n Jackson  with a trackball and a sneeze button, control a clown head on a stretchy neck in this nightmare fuel of a game
Space Bomber  hilarious and fun space invaders-esque game
Space Invaders 95: The Attack of Lunar Loonies  space invaders Parodius
Stone Ball - Soccer with very large cavemen using very large clubs
Survival Arts  another in a long line of hilariously bad Mortal Kombat imitations
Tapper  control a bartender trying to send the drunks under the table before they get you
Tattoo Assassins  one of MAMEs most glorious moments was adding this absurd Mortal Kombat clone that was never widely released to the public
Timber - guy from Tapper is a lumberjack and that's okay
Time Killers - the folks who made Golden Tee try to outdo Mortal Kombat by adding dismemberment and the result is hilariously terrible
Toki  control a spitting ape in this classic
Total Carnage  smash TV sequel that featured Saddam Hussein as an alien in disguise
Trio The Punch - Never Forget Me...  poster game for so bad its good, I cant tell if this was intentional or not
Uncle Poo  maze game with fart attacks, couldve been worse, I guess
Vendetta - Asia Version U - some versions of the game supports 4 players, but the Japanese (Asia Version U) 2 player version of the game has more hilarity *Warning* In addition to the absurd levels of violence present in all versions of this game, the Asia Version U adds extra homophobia and animal abuse, so steer clear if you don't want to experience that.
Vs. Block Breaker  Arkanoid clone where the balls are hamsters that splat on the ground and walk away
Wall Street  save suicidal stockbrokers and then steal money while destroying tanks with your magic powers
Wild West C.O.W.-Boys of Moo Mesa  what happens when a committee of executives dreams up a successor to Teenage Mutant Ninja Turtles
Windjammers  only slightly more ridiculous than ultimate Frisbee (seriously, though, Ultimate is fun and so is this game)
Wizard Fire  more over-the-top Data East goodness, mostly the cut scenes, though
Wonder Momo  mildly exploitative Japanese humor game starring a young woman fighting off masked weirdos onstage while an audience of men watches
Zero Team 2000 - beat 'em up that ticks all the boxes, exploding scenery and enemies, toilet paper and jewelry popping out of oil drums, cool nods to other games in the genre like Double Dragon and 4 player support ... the older game New Zero Team is only two players and has different levels, but is otherwise similarly fun
Zunzunkyou No Yabou  space invaders-esque with a lot of Japanese cultural idiosyncrasy