Zombie Attack
Man, a zombie infestation would suck in that, you know, loved ones dying, staying alive and such... but wow, what a kick-ass experience that would be. And rebuilding humanity!
If it did happen, though, I wouldn't want it to be a uni-federal thing, otherwise it might upset the balence of power, and then hell would break loose.
Great game, by the way. The only irk I have with it is that it seemed too easy for me. But it was fifteen minutes of fun, so 10s all around.