Warren Buffett is a mutual fund By: MarketWatch May 05, 2014 at 07:29 AM EDT Buffett’s success should make investors revisit one of the most basic investment decisions, whether to buy stocks directly, to invest in funds or to mix and match the two. Read More >> Related Stocks: American Express Berkshire Hathaway Coca-Cola Company Exxon Mobil International Business Machines Procter & Gamble Wells Fargo