Bill Gates was once the wealthiest man in the world according to Forbes magazine, a spot that he’s since lost to current numero uno Mexican businessman Carlos Slim. The former Microsoft (MSFT) CEO, though, may have lost the top spot because he’s dedicated his life to charitable giving. The Bill and Melinda Gates Foundation has funneled billions into improving education and healthcare around the world, including one project that has developed an early stage of a malaria vaccine. Gates has also tried to push other members of the uber-wealthy to offer up more of their assets to charity, and there are some that have answered that call.

Warren Buffett

This should come as no surprise, but Warren Buffett, a close friend of Gates, is one of the biggest givers in the country. Buffett, the CEO and Chairman of Berkshire Hathaway (BRK.A), is the third wealthiest man in the world (which, one could assume, Gates must tease him about constantly). However, he might be worth a great deal more if he weren’t in the habit of giving so much away. Buffett donated $1.6 billion in stock to The Bill and Melinda Gates Foundation last year, bringing his total to $8 billion. Oh, and there’s also the small matter of Buffett promising 83 percent of his vast fortune to the Gates Foundation in his will. That brings the total amount of money Buffett’s has pledged or donated to over $40 billion.

Buffett’s also the founder of The Giving Pledge, a pledge from billionaires to give away the majority of their fortunes in their wills. Buffett and Gates have approached dozens of the world’s billionaires in an effort to recruit them to the cause, and an impressive list of prominent billionaires have since signed on.

George Kaiser

Okay, so George Kaiser isn’t technically a CEO, but he is the independent Chairman of the Board for BOK Financial Corporation (BOK), and he is one of the biggest givers in the world. Kaiser’s The George Kaiser Family Foundation is dedicated to fighting childhood poverty. Over the course of his life, Kaiser’s donated or pledged over $2.5 billion.

The Walton Family

Mega-retailer Wal-Mart (WMT) was founded by Sam Walton and his eldest son, S. Robson Walton, remains the company’s CEO. Wal-Mart is notoriously cheap when it comes to its prices (and its employees’ health insurance), but the Walton family has been more than generous with its wealth.  Taken in combination, the Waltons have pledged or donated over $2 billion to the cause of improving education.

Robert Day

Robert Day, the CEO and former Chairman of The Trust Company of the West, is a very generous man.  Day, who founded Trust Company of the West before ultimately selling 70 percent of it to Societe Generale (SCGLY) for $2.5 billion in 2001, has pledged or donated over $300 million to various causes.

Larry Ellison

Larry Ellison is the co-founder and CEO of software company Oracle (ORCL), and to any members of the Occupy Wall Street movement he certainly looks like the enemy. Firmly a member of the 1 percent, Larry Ellison’s passions include yachting, driving his exotic cars, and flying his private jets. Yes, jets, plural. However, before you grab the torches and pitchforks, know that Ellison has pledged or donated over $800 million to charity over the course of his life. Ellison is also a signatory of Buffett’s Giving Pledge.