oh mr letterman ; the top 10 ways to destroy the earth

10 : Total existence failure
9 : Gobbled up by strangelets
8 : Sucked into a microscopic black hole
7 : Blown up by matter/antimatter reaction
6 : Destroyed by vacuum energy detonation
5 : Sucked into a giant black hole
4 : Meticulously and systematically deconstructed
3 : Pulverized by impact with blunt instrument
2 : Eaten by von Neumann machines

http://www.livescience.com/technology/destroy_earth_mp.html
and the number 1 way to destroy the earth is :
Hurled into the Sun
Method: Hurl the Earth into the Sun. Sending Earth on a collision course with the Sun is not as easy as one might think; even though you don't actually have to literally hit the Sun (send the Earth near enough to the Sun (within the Roche limit), and tidal forces will tear it apart), it's surprisingly easy to end up with Earth in a loopy elliptical orbit which merely roasts it for four months in every eight. But careful planning can avoid this.