Like Exxon Mobil, Chevron relied on its refineries to hold up its bottom line in 2012. When oil prices were climbing, integrated energy companies were urged to dump their low-margin refining units. But Chevron and Exxon didn't listen, and when crude prices dropped, the hedge paid off. Profits at Chevron's U.S. downstream operations jumped by a third year over year on increased supply of domestic energy. That wasn't enough to keep overall profits from slipping, however, as big bets on upstream ops, like natural gas exploration, have yet to pay off. --T.Z.
Wal-Mart retook the top spot, Berkshire Hathaway made the top five, and Apple grew enormously.