Paintown is an open source fighting game in the same genre as Streets of Rage and Teenage Mutant Ninja Turtles
PainTown is a 2d side scrolling beatem-up game based on the Sega Genesis game, Streets of Rage 2. This game is completely written from scratch and uses a modular system for loading new graphics.
Windows / Linux / Mac OS X
http://paintown.sourceforge.net/