http://en.wikipedia.org/wiki/M.U.G.E.Nhttp://unofficial-winmugen.jpn.org/If you've not the patience to read the wiki entry, it's basically a fighting game engine which is incredibly easy to manipulate, allowing for communities of gamers/programmers/etc to either create their own fighters or rip the sprites from another work and import them. It's basically
every good 2D fighting game ever, with your choice of silly manga/DBZ type guys included.
I just recently re-discovered this program after my little brother DLed it way back in the day and it's about 400x more developed than it was back then. For those of you who have no real moral objection to emulator software (which, in the strictest sense, this ISN'T; it just happens to be really
really good at pretending to be MvC) this is really a fantastic FREE piece of software. There's a whole lot of Capcom characters and a
shitpot of King of Fighters chars for whatever reason, and the occasional comedy pieces like Homer Simpson and Peter Griffin thrown in for good measure. Some stuff is really assy or just plain broken, but even some of the original characters are really brilliantly done. With a bit of patience you can sift through the shake (re: jigglypuff) and find the gold (re: pocket shin gouki, waaah).
Anyway, if you're a fan of 2D fighters and your computer was built after, like, 1996 (the engine hasn't really changed since 2001), then there's virtually no reason not to own this fucking awesome game. That is all.