Starcraft. When I can't use the Xbox, I alternate between that and Halo CE on PC. (Which I won today...for like the sixth time on Legendary)
I usually play Protoss, but my older brother asked me to play Zerg (My worst species) so he'd stand a chance. We basically tied for most of the game, then he had to go, so he turned over the match to my little sister. That was when I mutalisk rushed her, but I think that would have worked on him too.
It would just have taken 50% longer.