Warren Buffett

Known as the "Oracle of Omaha," Warren Buffett is one of the most successful investors of all time.

Buffett runs Berkshire Hathaway, which owns more than 60 companies, including insurer Geico, battery maker Duracell and restaurant chain 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 promised to donate over 99% of his wealth. So far he has given more than $45 billion, mostly to the Gates Foundation and his kids' foundations.

In 2010, he and Bill Gates launched the Giving Pledge, asking billionaires to commit to donating at least half of their wealth to charitable causes.