George Foreman
Credit: Dale de la Rey / Getty Images

Despite being a two-time World Heavyweight Champion and Olympic gold medalist, George Foreman might be best known for the George Foreman Lean Mean Grilling Machine, an electric grill he's been hawking with tremendous success since 1994. Better known as the Foreman Grill, the device efficiently cooks hamburgers and meats, draining the fat in the process – or toasts a great panini. Foreman became the pitchman, because his habit of eating burgers before bouts made him a natural and because he genuinely liked the product. As the now ubiquitous line goes: "It's so good I put my name on it!"

In 2009, Foreman released 'Knockout Entrepreneur,' a book about everything he learned in the ring and behind the scenes. His basic thesis was that aggressive effort would be rewarded. "The most common characteristic of a Knockout Entrepreneur is that he or she is a risk taker," Foreman wrote. "And a Knockout Entrepreneur is the person who gets the job done. He or she is not content to say, 'Well, I tried, and it didn't work.' He will keep fighting until he knocks out the obstacles barring him from success."

Estimated Net Worth: $250 million