NEW YORK: Wal-Mart Stores Inc. is once again leading Fortune's list of the 500 biggest US companies by revenue, as the world's biggest retailer succeeded in posting strong growth despite a challenging economy for its shoppers.

The Arkansas-based company posted revenue of $469.2 billion for 2012.

Exxon Mobil drops back to No. 2, but energy companies continue to dominate the list with Chevron, Valero Energy and ConocoPhillips' spin-off Phillips 66 all making the Top 10.

General Motors and Ford Motor both slipped in the annual ranking but remain near the top, in the company of General Electric and Warren Buffett's industrial conglomerate Berkshire Hathaway.

Apple has jumped 11 spots to crack the Top 10 for the first time, landing at No. 6, while Facebook debuted at No. 482.