End of Days

1. The Universe randomly implodes or something

2. Access to the internet somehow gets cut off, people go crazy, and one thing leading to another, civilization slowly collapses

3. Bioweapon

4. We somehow suddenly all lose all our knowledge and we mess things up

5. The Large Hadron Collider at CERN destroys the Universe

6. Whoever is running this simulation turns it off

7. Aliens eat us

8. Mass drought all over the planet

9. All species on Earth become sterile

10. Ice Age