In case you haven't heard, there's a fan-mod out there that combines gameplay from the original Doom with classic Mega Man goodness. Pretty much every classic character is playable, from Mega Man himself to rival Bass, to most of the Robot Master cast.
Version 4 is set to drop this weekend, including reworked classic stages like Bomb Man, new weapons, new items, and additional maps. There's also a new campaign. I can't think of a better (free) way to spend your weekend!
Mega Man 8-bit Deathmatch [Cutstuff.net]