I had my fifth driving lesson when this happened. My driving instructor was completely losing his shit when when we heard it on the radio and panicked when the second plane hit. I was like "dude, this is really nasty but people do this to each other all the time".
ZOMBIE apocalypse would be awesome but sadly as always an antidote would be found and then the doctor would be all like "i am king of the world" and would live in a huge tower block at the top with all soldiers around and then would sell the antidote for cash or goods collected from the zombie infested world outside the city walls that he built to keep people safe but charge them fortunes to live within. You know, that old story!
Aliens would be bad as they would first come here in the guise of keano reaves and say shit like "your planet?" and the americans will instantly attack it for no reason then it would destroy the world but stop it last minute as the aliens realised that humans are capable of love and only change at the last monent.
and as for Nuclear. Have you played fall out 3? it wont be a war for oil. It would then be kill for food while groups of mutant bandits scour the wastelands for food and humans to eat. Humans would survive but one blind man with the only bible left on earth would be all like "hey this is my book, and i can fight like a ninja" and kills everyone who is trying to get the bible.
Killer bees would be unpleasant but at least we would have honey to eat if all went pear shaped.