Forbes Magazine said Wednesday Microsoft Corp. co-founder Bill Gates, worth $59 billion, was the richest U.S. citizen in 2011. The list that provokes gasps, curses, drooling and low whistling is the 30th annual ranking of the country\'s 400 wealthiest citizens. Warren Buffett, for years a top gun on Wall Street as the head of investment firm Berkshire Hathaway, came in at No. 2 with $39 billion. He recently made headlines by writing an editorial that said he and many of his ultra-rich friends should pay higher taxes to help \"while so many are suffering.\" Oracle Chief Executive Officer Larry Ellison was No. 3 at $33 billion. Koch Industries Chief Executive Officer Charles Koch and his brother David Koch, an executive vice president of Koch Industries also known as \"New York City\'s richest resident,\" rounded out the Top 5 at $25 billion apiece, Forbes said. The Top 10 includes three Wal-Mart heirs -- Christy Walton, Jim Walton and Alice Walton, with a combined wealth of $66.5 billion -- investor George Soros and Las Vegas casino mogul Sheldon Adelson. The richest politician on the list was New York Mayor Michael Bloomberg, worth $19.5 billion. The youngest billionaire at age 27 was Facebook founder Mark Zuckerberg, No. 14 and worth $17.5 billion.