IK+, best fighting game ever made .
http://www.youtube.com/watch?v=q4ph2nP6l7c simply awesome .
http://amigareviews.classicgaming.gamespy.com/ik.htm
Seconding the love for MUGEN. It has a ton of custom user-made characters, from popular fighting characters to people like Homer Simpson. It's ace.M.U.G.E.N was the game I was referring to earlier.