1. Meteor collision.
2. Blasted by aliens.
3. Atmosphere suddenly goes.
4. Global warming.
5. Nuclear war.
6. Tipped out of orbit.
7. Moon implodes.
8. Black hole sucks us in.
9. Sudden solar flares burns us out.
10. Sudden proliferation of vampires and zombies.
11. Invasion of body-snatchers.
12. Alien germs suck out cerebra.
13. Global cooling.
Patruus