[Dismas]

2D fighting game that you can import characters into. They have many from decent anime/etc. out there.

M.U.G.E.N (also known simply as MUGEN) is a freeware 2D fighting game engine designed by Elecbyte. Content is created by the community, and thousands of fighters, both original and from popular fiction, have been created. It is written in C and originally used the Allegro library. The latest versions of the engine now use the SDL library.

https://en.wikipedia.org/wiki/M.U.G.E.N