I guess I'm in. I hope I don't disappoint!
General Likes:
Mockups.
Sprites.
Low bits per pixel palette and tile based things. Think NES, Game Boy (Color), or Sega Master System.
Animation.
Games/Characters that are cool:
Gunstar Heroes
Portal
Metroid Series
Super Smash Bros. Melee
Wario (Adventuring Wario, not Wario Ware Wario)
Mr. Game and Watch
Sakura Kasugano (Street Fighter)
Shy Guy
Bomberman
Dislikes:
Hmm... no blood or gore. That's not too interesting to me, and is the only hard rule. Cartoon violence is totally fine.
Really jarring palettes. (Default 16 color EGA comes to mind. But if you don't know what I mean by jarring palettes, or ROCK the EGA palette go for it.)
Dithering, generally. (But again, if your whole style is dithering, go for it.)
Really, though, most things are fine. I like all manner of pixel art, whther it's 56 colors and what some may complain is Oekaki/rough, or whether it's a carefully controlled 32/16/8 or 4 color piece. The characters/games are there in case you wanted some ideas besides, "Do whatever." Feel free to make something totally original that includes none of it.