Source: Flickr user Moodboard.

One of the biggest mistakes senior citizens are guilty of these days is investing too conservatively or simply halting their investing activity once they retire. Considering the stock markets' superior long-term return potential compared to CDs and bonds, as well as the fact that seniors are living longer than ever, it pays for senior citizens to remain invested in the market.

With that in mind, we asked three of our analysts for one stock they believe could benefit seniors, and which they could consider buying right now. Here's what they had to say. 

Selena Maranjian: A company that should interest senior citizens is MetLife Inc. (NYSE:MET), one of the world's largest life insurance companies. (It's a bit of a senior citizen itself, founded in 1868!) It boasts about 100 million customers in almost 50 nations, offering life insurance, annuities, asset management, auto insurance, home insurance, IRAs, employee benefit programs, and more.

The company is moving into fast-growing emerging and developing markets, and is profiting from it. For example, operating earnings in its European, Middle Eastern, and African business (excluding Western Europe) grew 16.1%, on average, over the last two full financial years.

Source: MetLife.

MetLife is looking to boost profitability through cost-cutting, while reducing operating earnings volatility and improving free cash flow by shifting its business focus from market-sensitive, capital-intensive products toward protection-oriented, capital-efficient products. (For example, it's growing its employee benefits management business, while variable annuity sales are shrinking.) It's hoping to benefit from expected growth in interest rates in coming years, too.

In its last quarter, the company's operating earnings exceeded analyst expectations, growing by 22% year over year. That's faster growth than its premiums, fees, and other revenue, which grew by 8%, and suggests that its cost-cutting and profitability-improving strategies are working.

MetLife's valuation is quite appealing, with its price-to-earnings ratio recently 11, near its five-year average, and below the industry average. Its forward-looking P/E, based on next year's expected earnings, is around nine. With a market capitalization near $63 billion, MetLife is a financial giant with a diversified international platform, economies of scale, and a well-known brand. It offers a dividend that recently yielded 2.5%, too.

Dan Caplinger: Many senior citizens have a long relationship with Ford Motor (NYSE:F), whose vehicles pioneered the automotive industry and have enjoyed a long history with the American public. As the only member of the Big Three automakers not to take a government bailout or go through a bankruptcy proceeding during the financial crisis six years ago, Ford has demonstrated its ability to manage its business well while also taking advantage of favorable industry trends and moving forward with its own initiatives.

For more than five years, Ford wouldn't have looked nearly as attractive to older investors, as it had to suspend its dividend during tough times. Now, though, Ford's quarterly payouts are back, and with a yield of more than 3%, retirees can count on receiving a nice paycheck from their investment in the automaker over the long run.

Source: Ford. 

Recently, Ford has been in the process of introducing some huge new updates to its popular models, including the groundbreaking aluminum-rich F-150 pickup. Some have seen this move as a risk, but the short-term hit to earnings is likely to pay off with faster growth down the road. With shares at a bargain price of just 10 times trailing earnings, Ford looks poised to accelerate into the future, giving older investors both the security of a blue-chip name and the income and growth potential they need from an investment.

Sean Williams: When thinking about a stock seniors could buy right now without losing sleep at night, I'm looking for a company with a well-rooted dividend and an easily recognizable brand that they can identify with. One that certainly fits the bill is beverage behemoth Coca-Cola (NYSE:KO).

We have to remember that today's senior citizens grew up in a different era where war was common and patriotism was arguably worn on one's sleeve a lot tighter than we see today. A Brand Keys study conducted this past summer showed that Coca-Cola ranked third in terms of America's most patriotic brands. This leads me to believe Coca-Cola would generate a strong emotional connection with seniors, and would also serve the purpose of driving consumers in the U.S. to the brand.

Beyond the borders of the U.S. Coca-Cola is instantly recognizable, with 94% of world's population able to recognize its red and white logo. Furthermore it's well-diversified, operating in all but two countries worldwide and with enough products that it would take a person more than nine years to try them all if they sampled a new one each day.

Source: Coca-Cola.

This product and geographic diversity leads to one thing seniors are bound to love: a 52-year streak of rising dividends. Only a few dozen companies have successfully raised their dividend for 25 straight years, and Coca-Cola is among the top-tier of that group with a yield that's just shy of 3%.

Coca-Cola also boasts a beta of just 0.68. In layman's terms this just means that Coca-Cola is only 68% as volatile as the S&P 500. Sure, it could mean underperforming when the market is soaring, but it also means less overall volatility for seniors.

Lastly, Coca-Cola's products are relatively inelastic. This means demand tends to not slow much even in deep recessions, leading to somewhat predictable cash flow and profitability for the beverage giant. 

Selena Maranjian and Dan Caplinger own shares of Ford, but have no material interest in any other companies mentioned. Sean Williams has no material interest in any companies mentioned. 

The Motley Fool recommends Coca-Cola and Ford. The Motley Fool owns shares of Ford and has the following options: long January 2016 $37 calls on Coca-Cola and short January 2016 $37 puts on Coca-Cola. Try any of our Foolish newsletter services free for 30 days. We Fools may not all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors. The Motley Fool has a disclosure policy.