Global 500

Wal-Mart Stores maintains its perch atop the corporate ladder, taking the top spot on this year's Fortune's 500 and Global 500 lists, both for the second year in a row.

A company that big makes big headlines, both good and bad. For example, Wal-Mart continues to receive credit for its role as a leader in corporate sustainability. The company launched its "Sustainability Index" in 2009 in an effort to assume accountability for its products' origins and to make that information transparent to customers.

But Wal-mart has also been in the spotlight this year for a gender discrimination suit involving 1.5 million of its current and former female employees. The Supreme Court threw the case out on the grounds that the women couldn't pursue it as a single class, but the retail giant will likely have to face these claims in smaller groups in the months and years to come.

And while Wal-Mart may be the biggest company in the world, it has suffered from a sales slump back home: U.S. same-store sales have declined for eight straight quarters. --By Shelley DuBois, writer-reporter