Warren Buffett and his right-hand Charlie Munger seem sweet on the world's largest company, Apple (NASDAQ: AAPL). But that's not the only stock his company, Berkshire Hathaway (NYSE: BRK-A)(NYSE: BRK-B), has recently bought. The legendary investor also added to his positions in several big banks according to recent 13-F filings.But Buffett didn't just buy.