Humans only use approximately 10% of their brain?

*Reving up a chainsaw* What 90% do you think i can cut out?Its a myth like god I think the mythbusters also tacled this one and even when we do nothing and think of nothing we use more then 10% of our brain.

He probably meant that we dont "train" our brains very well and that our capacity for learning understanding reasoning and so forth could be much grater if we actually use our brains once in a while If you compare the brain to a muscle if you dont use it it becomes weak if you use it like some train their muscles to become like Schwarzenegger your mental capacity could be 10 times grater.