Known as the "Oracle of Omaha," Buffett is one of the most successful investors of all time. His Berkshire Hathaway owns more than 60 companies, including Geico, Duracell and Dairy Queen. The son of a U.S. congressman, he first bought stock at age 11 and first filed taxes at age 13. He has committed to giving more than 99% of his fortune to charity. So far he has given $28.5 billion. With friend Bill Gates, he launched The Giving Pledge, asking billionaires to donate their wealth.