In 1997, shortly after selling his cable empire to Time Warner, media mogul (and CNN founder) Ted Turner pledged $1 billion to the United Nations.

"I am absolutely certain we would not have made it through the Cold War without the UN," Turner told Reuters in 2006. "When Khrushchev at the UN took his shoe off and hit the podium ... he had a place to let off steam. If the UN hadn't been there, that would have been war right then."

Turner specified the money was not to be used for general administration, but rather programs geared toward land mine removal, refugees and peacekeeping.

At the time, his gift made him the largest single contributor to an organization. It also prompted him to chide fellow billionaires Warren Buffett and Bill Gates for not giving more to charity -- criticism they evidently heeded. Gates and Buffet went on to found The Giving Pledge, an informal commitment by the world's wealthiest people to donate the majority of their fortune to charity.