What boulder said. I don't want to deal with zombies or some kind of "rage virus" (no, just because The Walking Dead is fun to watch doesn't mean a zombie apocalypse would actually be fun), I don't want to deal with a deadly plague, and I don't want to deal with nuclear war.
So that leaves collapse of society... still pretty bad, but fortunately not many people around my area have guns... and I do. Normally I like firearms, but in an apocalypse I don't want to run into random hungry people with guns, sorry.