Warren Buffett’s Berkshire Hathaway recently cut its positions in several stocks, including IBM and Oracle. But Berkshire remains invested in dozens of other stocks, and some of them are still worthy buys for mainstream investors.Today, a trio of our Motley Fool contributors will highlight three of their favorite Buffett holdings: Costco (NASDAQ:COST)Apple (NASDAQ:AAPL), and Phillips 66 (NYSE:PSX).