In the fight to top the latest Fortune 500 list, it's Big Oil from Irving, TX vs. Big Plastic from Bentonville, AR. Here's who wins:

Skyrocketing energy prices propelled Exxon Mobil Corp. to the top of the 2006 Fortune 500 list, and consigned Wal-Mart Stores Inc. to the No. 2 spot on the magazine's annual ranking of the nation's largest publicly traded companies.

Fortune compiled its list based on companies' 2005 revenues. Exxon Mobil raked in $340 billion in revenue, a 25.5 percent increase over 2004, and had $36.1 billion in profits, the most by any U.S. company in history.

And for those who still think free competition is the name of the game in U.S. capitalism, here's a fascinating statistic:

Exxon Mobil last appeared at No. 1 in 2001. Only Wal-Mart, Exxon Mobil and General Motors Corp. have topped the list since its inception in 1954.

And if there are any doubts about which sector of the economy drives the U.S., here's another:

Pipelines, Internet services and retailing, petroleum refining and mining-crude oil production were the fastest-growing industries of 2005.

What was that about our addiction to oil?