Wal-Mart nosed out Exxon Mobil for the second consecutive year to land atop the 2008 Fortune 500, with $37.7 billion in revenues, the magazine said today. In profits, the oil company far outstripped the megaretailer. Three of the top 5 on the list were oil companies, the AP reports. ChevronTexaco (No. 3) and GM (No. 4) swapped places, and ConocoPhillips again rounded out the top 5.