Asteroid Apophis is last on our list, and certainly not the best. It is, after all, named after the Egyptian god of "uncreation" for a reason.
Known in scientific circles as both 2004 MN4 and 99942 Apophis, this 885-foot-long space rock used to have a fairly good chance of impacting the Earth within a quarter century.
After making a breathtakingly close pass on Friday the 13th in April 2029 -- less than 10 percent of the distance between Earth and the moon -- Apophis was thought to have a 1 in 45,000 chance of hitting Earth in 2036 when it swings back around.
However, recent calculations have reduced this risk to a 1 in 250,000 chance. Phew!
Despite Apophis' diminished threat to Earth, some scientists advocate sending a transmitter to the asteroid's surface to better track its movement. And now, Russia wants to send a deflection mission there, 'just in case' the calculations wrong.
Slide show presentation originally compiled by Dave Mosher.