Super Mario Bros. Crossover 2.1\
Super Mario Crossover (Version 2.1). Somebody ported Super Mario Brothers, and made it so you could be a whole lot of other retro video game characters. Samus, Megaman, Link, and more! It's a ton of fun. In the latest version they have a lot more skins for the levels, enemies, and characters. Certain skins for the characters have separate abilities, which is pretty sweet. Try it, if you haven't.