A large chunk of stone, iron or ice screaming through space. At some point in time the orbit intersects a planet. KERBOOM! There go the dinosaurs! KERBOOM! There goes New York! Visit the showroom to see our demonstration models. Then take one for a spin!

Check this out: anything below 500 meters diameter shouldn't cause too much damage. Earth's atmosphere provides some protection. Can't say the same for the Moon or Mars though. A 2 kilometer brick packs 20 megatons on impact and can cause severe environmental damage on a global scale (talking of Earth of course). Up in the 15 km range you are looking at mass extinctions and the loss of civilization. Vesta, the largest asteroid in the asteroid belt, is around 600 km in diameter. For the record, Vesta is not available for purchase.

On Earth there are more people searching for Elvis than are searching for possible Doomsday Asteroids.