Super Mario Crossover
Play the original Super Mario Bros. game with Mega Man, Samus Aran, Link, Simon Belmont, or the guy with blue pants from Contra.
I wish I could find a way to use an old NES controller with my computer. I'd have beaten this thing. Instead, I lost both my lives in World 1-4, both with Mega Man.
Still, it's amazing fun. Going to have to try it with Simon Belmont now.