ExxonMobil (NYSE:XOM) ranked in second place behind retail giant Wal-Mart (NYSE:WMT) in this year's Fortune 500. However, what you probably don't know is that the No. 1 spot has gone to one of the same three companies -- Exxon, Wal-Mart, or General Motors (NYSE:GM) -- each year since 1955.

In fact, this year marks Wal-Mart's ninth time at the top, whereas Exxon has claimed the top spot for 13 years and GM a whopping 37 years in total. Ranked by revenues, the Fortune 500 list is an annual compilation of America's largest companies. It's not surprising then that Exxon was one of the original Fortune 500 companies, and has been on the list every year for the past 58 years.

How long will the stock be on top?
ExxonMobil stock has gained 5% for the year. This isn't great for a stock that trades at just nine times earnings and boasts a dividend yield of 2.7%. It's true that the sheer size of ExxonMobil's business makes it difficult to show impressive year-over-year earnings growth. However, ExxonMobil stock is on the money when it comes to allocating capital.

In addition to the stock's historically high returns on capital, ExxonMobil knows how to reward its shareholders. In fact, ExxonMobil has paid out more than $40 billion in dividends and repurchased $100 billion worth of stock in just the past five years, according to Morningstar. It's tough to beat that level of shareholder return.

Wal-Mart may have taken back the No. 1 seat this year, but ExxonMobil was still the most profitable stock on the list with revenue of $449 billion. At the end of the day, ExxonMobil stock looks like a core energy play for conservative long-term investors.