If Mega Man 8-bit Deathmatch isn’t the greatest thing of all time, it’s really really close: "
Apparently this has been in development for quite some time, as a mod for a modern port of Doom called Skulltag. It allows you to play as any of the 48 robot masters from the first six Mega Man games. Unfortunately, while you’ll fire the weapons associated with the boss (metal blades, cut boomerangs, etc), they won’t have their respective effects on other guys — they’re all just the basic arm cannon with some modifications. That’s disappointing, but if this blows up (it’s slated for a free 2010 release) maybe we can get it expanded on.