Wal-Mart (WMT) has regained its place at the top of the Fortune 500, marking the fifth time in the past six years that the retail giant has headlined the list of the largest companies in the U.S.

The Arkansas-based retailer saw revenues climb 11 percent since last year, and employs an astounding 1.9 million people worldwide. And while the behemoth has its share of image problems, it has launched a public relations campaign aimed at improving its standing in the eyes of consumers.

Last year's No. 1, Exxon Mobil (XOM), slipped to No. 2 on the list, but still boasted the best profits of any company, at $39.5 billion for 2006.

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