We planned to do a blowout of Neo Geo cheats in celebration of the all-Neo Monday, but forces conspired against us. First, there just aren't that many codes for the Neo Geo games released this week. That's the biggest problem. Second, Neo games may not even display properly on your TV, meaning that a lot of people may not even be able to play them, much less play them using advanced cheaterly techniques.
So, instead of a blowout, you get ... two unlockable characters in Art of Fighting.
Unlock Mr. Karate: Do you want Mr. Karate? Then when you reach him in the single-player mode, lose. (Which, against SNK bosses, is the default state.) Start a two-player game and Mr. Karate will be available.
Unlock Mr. Big: It's true*. You can play Art of Fighting with the band responsible for the hit ballad "To Be With You". They all move in unison. It's a little weird. You access Mr. Big in the same way you play with Mr. Karate: by losing to him, then starting a two-player game.
*By "true", we mean "not true".
[Codes via GameFAQs]