http://www.arcadiaclub.com/img/imgames/gc/mugen.JPG
Ever wanted to put any character from any series and have them fight? This is the program for you.
Street fighter VS Mega Man VS Super Mario Brothers VS Dark Stalkers VS Guilty Gear VS DBZ VS Naruto VS Sailor Moon VS EVERYONE!
You can look up basic detail on wikipedia at http://en.wikipedia.org/wiki/M.U.G.E.N
Otherwise, post your favorite video from YouTube or whereever. I've seen videos who had rosters up to like 300 people haha. Here's a few videos to get you started.
http://www.youtube.com/watch?v=PCDFgp4NWZ8 - Roster Video
http://www.youtube.com/watch?v=-rvVkYpC5VI - Mario Bros VS Mortal Kombat
http://www.youtube.com/watch?v=ySbe0gdg0DI - Homer Simpson VS Jill Valentine
To get this program....just search around. I'm personally downloading a pack from ISOHunt. The basic program can be found at http://unofficial-winmugen.jpn.org/