This almost ended up on the Weird Factor, but it's a game, so it goes here:
The Kill Everyone Project is a game, with a chat feature that lets you virtually kill everyone on earth with mouse clicks. The site is not sure what happens when the last click is made, but they think it may look like this.
If you need some FaQ style help, hit up the How Do I Kill site.
The site includes tags so you can tell the world on your website exactly how high your body count is.