Fortune 500: See who's No. 1

The retail giant knocks Exxon Mobil out of the top slot to rule the Fortune 500 again. See the full list of America's largest corporations.

NEW YORK (AP) — Wal-Mart Stores Inc. once again leads Fortune's list of the 500 biggest U.S. companies by revenue, as the world's biggest retailer succeeded in posting strong growth despite a challenging economy for its shoppers.

Wal-Mart takes the top spot on the Fortune Global 500 for the second year in a row. See the full list of the world's largest corporations.

Wal-Mart Stores Inc., the world’s largest retailer, reclaimed the top spot from Exxon Mobil Corp. in the Fortune 500 ranking

By Income Hunter:Exxon Mobil (XOM) started May with a bang on news that it slid back into the number one spot on the Fortune 500. Since 2006, under the guidance of CEO and Chairman of the Board Rex W. Tillerson, Exxon Mobil has flourished.

ByCatalyst Investments:Exxon Mobil (XOM) is the world's largest company by market capitalization, the #2 business in the Fortune 500 (for 2012, behind another oil company, Royal Dutch Shell (RDS.a)), and a giant in the oil an

ByTiming Best Buy:Incorporated in 1882, Exxon Mobil (XOM) is a behemoth in the major integrated oil and gas sector. The company's principal line of business is energy as it explores for, produces, transports, and markets crude oil, natural gas, and liquefied natural gas (LNG) in the U.S., South America, Canada, Europe, Asia, the Middle East, Australia, and Oceania.