It's always a good idea to look inside Berkshire Hathaway's stock portfolio, because Buffett is one of the greatest investors of all time.Warren Buffett needs no introduction. The 94-year-old is widely considered one of the greatest investors of all time, having built his company Berkshire Hathaway into the sixth largest publicly traded company in the world.Within Berkshire is a more than $300 billion equities portfolio that the Oracle of Omaha, with the help of his investing lieutenants, has built from scr ...