Big Oil doesn't get much bigger than ExxonMobil (NYSE:XOM) -- the largest energy company in the world not owned by a government. Just how big are we talking about? According to a Reuters news item I saw this morning, Exxon's annual profit this year surpasses the size of 125 of the 184 national economies listed by the World Bank.

That's pretty big.

Speaking of profits, this was another banner quarter for Exxon. Sales were up 19.5% in the fourth quarter as strong earnings from the upstream exploration and production business (fueled by higher crude oil and natural gas prices) offset sluggishness in the downstream refinery business. Excluding various special items, net income rose 23% and diluted earnings per share were up 27% for the quarter.

Upstream earnings growth led the way this quarter, with earnings here up 44% as the company counterbalanced slight production shrinkage with much higher oil and gas prices. Total production was reported down about 1% on an oil-equivalent basis, but would have been up 2% without the impact of Hurricanes Katrina and Rita, as well as excluding certain divestments.

In the downstream business, higher refining margins couldn't completely offset lower throughput. Earnings for the unit were up just 2% for the quarter, though earnings from U.S. operations were up a gaudy 32%. Chemicals continued to have a rough go of it, with earnings excluding special items falling by one third from last year's fourth quarter.

As big as Exxon is, there's still room for more. The company has just started to really get its liquefied natural gas (LNG) business going and, though it's heavily dependent upon Qatar, an acquisition of someone like BG Group (NYSE:BRG) or Marathon Oil (NYSE:MRO) could speed its LNG program along. Even if Exxon doesn't do deals, though, the company still sports low finding and development costs, has production ramping up in West Africa, and possesses meaningful upgrade capacity in its refineries.

I don't think Exxon is too expensive today, though I'd be tempted to wait for an inevitable short-term slide in oil prices before buying the stock. There are all sorts of high-quality plays in the energy space, though, ranging from ExxonMobil to Occidental Petroleum (NYSE:OXY) on down to XTO Energy (NYSE:XTO) and Ultra Petroleum (AMEX:UPL), so do your own due diligence and find what you think is the best mix of value, risk, and dividend growth for your own situation.

For more energy Foolishness pumped from our archives:

Fool contributor Stephen Simpson has no financial interest in any stocks mentioned (that means he's neither long nor short the shares).