Who where the biggest "GIVERS" of 2012?!

Last year's 15 biggest gifts to charitable causes by American billionaires added up to more than last year's, but of that total more than half came from one man.

Warren BuffettWealthy Americans gave $5.1 billion dollars in the 15 biggest charitable donations of 2012, according to the "Chronicle of Philanthropy." But subtract the $3 billion pledged by Warren Buffett, and the total would be far less than last year's $2.6 billion.

(Read more: Majority of Wealthy Support Taxing Themselves More, Poll Says)

The top givers were:

1. Warren Buffett: $3.09 billion in stock to be divided equally among three foundations run by his children
2. Mark Zuckerberg: $498.8 million to Silicon Valley Community Foundation to support education and health
3. Paul Allen: $300 million pledge to the Allen Institute for Brain Science
4. Mortimer Zuckerman: $200 million pledge to the Columbia University's Mind Brain Behavior Initiative
5. Fred Fields: $150 million bequest to Oregon Community Foundation to support art and education
6. Carl Icahn: $150 million pledge to Mount Sinai School of Medicine for medical research

Three of those top gifts were announced in December - either a good sign for 2013, or an effort to avoid the effects of the fiscal cliff.