The motivations of the signatories beyond this are as broad as their businesses. Buffett, known as the Sage of Omaha for his investment prowess, has not used his stock-picking abilities to single out particular charities, but expects his fortune to be used within a decade of his death. "I want my money spent on current needs," he has said.
Mark Zuckerberg, on the other hand, used the giving pledge last year to commit to long-term projects "that will take a decade or longer to reach their goals". The Facebook founder and his wife Priscilla Chan recently set up an initiative to cure diseases.
Elon Musk, Richard Branson and George Lucas are among the other super-rich who have signed the giving pledge. Many signatories said they were already giving away money quietly, but the billionaires' call persuaded them to set an example.
Blockbuster donations to charity are relatively rare, but their impact can be enormous. According to the banking firm Coutts, there were 355 donations in Britain that broke the 1million (1.78m) barrier last year - up from 298 in 2014. These gifts brought a total of 1.83b to 267 different institutions, with about a third going to universities.
This is a significant slice of the 10b that the Charities Aid Foundation estimates individual Britons gave away last year.
One of the biggest donors, Lord Sainsbury, gave more than 60m to his long-running Gatsby Charitable Foundation. The supermarket scion, who has also signed the giving pledge, cites his time as a Cambridge undergraduate for his commitment to investing in neuroscience research.
Other philanthropists use their time to gather others around them in their charitable work. Michael Spencer, who founded the trading firm ICAP, helped to raise 8.2m last week during the firm's annual charity day.
ICAP hauled in everyone from Prince Harry to Tom Hardy to work alongside fancy-dressed traders for the day, before donating the proceeds, amounting to 4 per cent of the last year's pre-tax profits, to various causes. Over the past 24 years, the charity day has cast its net wide, supporting 2200 different causes from cataract surgery in India to a missing persons hotline in Europe.
"By selecting a limited group of charities, which tend to be on the smaller end of the scale, we can make a sizeable donation," said Spencer of the annual donation process.
"We hope this will have a transformational impact and will allow the charity to launch new projects and build their operations. What is most important is that they are efficiently run and have a proven track record."
Some in the world of finance tie their companies to philanthropic work in an even more direct way. The Children's Investment Fund was set up to donate a portion of its proceeds every year to a charitable foundation aimed at tackling childhood poverty. "I want to solve problems, not make grants," says founder Sir Chris Hohn of his charitable work.
For those who graduate from a City job into the realm of multi-millionaire, philanthropy is often a big part of their financial planning.
Having such resources - at least "a couple of million to make it fly", says Jean-Philippe Krafft, senior wealth planner for Pictet Wealth Management - enables wealthy families to set up their own trust and target donations.
"Families tend to want to do direct investments, avoiding big structures and intermediaries. They like to help directly and have direct contact with the beneficiaries or organisers."
Abseiling down skyscrapers in London has become a popular way to raise money for thrill-seeking financiers, including the Lord Mayor of London, who raised 1.1m in his charity appeals last year.
City Bridge Trust, the charitable wing of the City that dates back to the 13th century, has also been going skyscraper to skyscraper, holding an event recently for staff in numerous businesses in the Walkie Talkie tower.
"Although these people probably share a lift together most days, they never speak. But they can come together for this giving agenda and recognise what others are doing," said David Farnsworth, the trust director.
He said the examples of enormous donors such as Buffett and Zuckerberg are helpful, albeit remote, ways to encourage giving. "I think that raising the profile of the giving agenda is positive. But it's important it's not just seen as the preserve of the wealthy. We're trying to encourage a sense of democratic ownership in projects."
