Focusing on fun NES titles:
10-Yard Fight - Made me laugh. Football game.
720° - So overly simple. Skateboarding game.
8 Eyes - 8 eyes sounds pretty creepy. CV-style game.
Adventure Island - I have good memories of this one. Adventure Platformer.
Airwolf - An air-elemental wolf shirt design? Sweet. Shooter game with a helicopter but I've personally heard of it before so it wasn't TOO obscure.
Anticipation - THE ANTICIPATION!!! A connect-the-dots trivia/puzzle game. Best music evar! Best video game cover expressions evar!!! http://www.youtube.com/watch?v=OBNaVhpoAr8 (Ahem, anyways)
Balloon Fight - Yeah, I mentioned it before, but I still think it'd be a great shirt design. :P Arcade-style game.
(The) Battle of Olympus - Could be a fun shirt I guess but I mostly just wanted to talk about this one cuz of the music. :D
Bubble Bobble - Somehow. Arcade-style game.
Chubby Cherub - Well maybe not. :P Platformer thing.
City Connection - Could be a fun design? Really weird arcade-style game.
Clu Clu Land - Rejectionator Bait. ;P
Color a Dinosaur - For those who really want to make a Dinosaur shirt. It is legitimately a game of coloring dinosaurs.
Crystalis - RPG
Double Dragon - For those who want to draw shiny dragons. Beat'em'up game.
Excitebike - Seems like it'd have potential. Racing game.
Gauntlet - Doable. Arcade hack and slash.
Ice Climber - Climb that ice! Platformer.
Joust - Someone else mentioned it but you must include ostriches. Arcade-style game.
The Last Starfighter - What, it's a game, too. Mostly avoiding tie-in games in this list of ideas, but this one WAS a video-game in the movie as well sooooo.
Lemmings - Can't go too wrong with suicidal rodents. Puzzle Platformer.
Life Force - Use the Force to beat the game of LIFE? LOL silly people. Shooter game.
Maniac Mansion - A challenge.
Monopoly - Also been skipping on stuff like this but I can't help but think about the Monopoles in Robotics;Notes. Monopole'y.
Mystery Quest - Hah.
Kay I'm gonna get lazy for the rest of these.
Pipe Dream - WOO, Pipe Dream! :D Old school favorite.
Shadowgate - This is one most people have heard of before, right? :P
Snake Rattle 'n' Roll - Mmmmm, Snakey.
Spelunker - *trips, dies*
Swords and Serpents
Werewolf: The Last Warrior - ... Heh. Fuzzball.
Wizards and Warriors
Edit: Unlicesed, for the Lulz
Big Nose Freaks Out
Challenge the Dragon
Dizzy the Adventurer
Dudes with Attitude
King of Kings: The Early Years
Secret Scout in the Temple of Demise
Trolls on Treasure Island
Wally Bear and the NO! Gang (*snrk*)