Brock Lesnar -- Beaten Into Retirement

Brock Lesnar knows when to hang it up. He announced he was quitting the whole MMA thing after suffering a lightning fast loss to Alistair Overeem last night at UFC 141.

Lesnar was floored by a brutal kick to the stomach and the fight was stopped at the 2:26 mark of round one. He said after the fight, "I've had a really difficult couple of years with my disease, and I'm going to officially say tonight is the last time."

The former pro wrestling star fought only three times in the last 2.5 years while battling a lower-intestinal disease that nearly killed him.