Costco's  (NASDAQ:COST) Jim Sinegal is not your typical CEO. He spends the majority of his time visiting his stores, not in his office. He deals with customer complaints directly. And he gets criticized on Wall Street for being too generous to his employees. (Sinegal says that Costco’s decision to pay its workers more than Wal-Mart (NYSE:WMT) is good business, not altruism.) 

When he stopped by FoolHQ in July, we asked Whole Foods (NASDAQ:WFMI) CEO John Mackey what his biggest weakness was. When Sinegal was here, we put the same question to him.