Unavoidable, like a big-ass meteor?
Party HARD. Then grab a shotgun and get things done my way one last time.
Avoidable, like a nuclear war?
Oh well. Buy more food, alcohol and ammo, place sandbags all around the basement, make sure fallout has no way of getting inside, grab an oil lamp, some candles and enough books to last me 2 years, bring a radio, a tv set and my computer/playstation (oh well, maybe somehow the EMP wouldn't get there

), some comfy stuff for sleeping and wait for it brooding about how fucked up the world is.