Warren Buffett is in a giving mood -- and when Buffett gives, he really gives. The billionaire investor has donated $1.25 billion in shares of his Berkshire Hathaway ( BRK-B) to the charitable organization run by Microsoft ( MSFT) founder Bill Gates and his wife, Bloomberg has reported. Buffett donated 428,688 shares of Berkshire, valued at $2,924 each, at the close of trading on Wednesday, according to a regulatory filing. This is the latest gift Buffett has made to the Bill & Melinda Gates Foundation. He made a pledge in 2006 to give a hefty chunk of his fortune -- about $30.7 billion on it -- to the organization, which focuses on education and global health.