"I can't die. It would ruin my image."

Jack La Lanne 

The original Birthday Challenge guru. This guy is still kicking ass in his 80s, and it sure as hell doesn't look like he's going to stop anytime soon. During a recent interview on The Larry King Show, Jack was so aggro he didn't sit still for the whole interview. We could go on forever on the Challenges he's done in the past, but instead read about it yourself.