Here at Zacks, we focus on our proven ranking system, which places an emphasis on earnings estimates and estimate revisions, to find winning stocks. But we also understand that investors develop their own strategies, so we are constantly looking at the latest trends in value, growth, and momentum to find strong companies for our readers.Considering these trends, value investing is clearly one of the most preferred ways to find strong stocks in any type of market. Value investors rely on traditional forms of analysis on key valuation metrics to find stocks that they believe are undervalued, leaving room for profits.In addition to the Zacks Rank, investors looking for stocks with specific traits can utilize our Style Scores system. Of course, value investors will be most interested in the system's "Value" category. Stocks with "A" grades for Value and high Zacks Ranks are among the best value stocks available at any given moment.One company to watch right now is Cigna (CI). CI is currently sporting a Zacks Rank of #2 (Buy), as well as an A grade for Value.We also note that CI holds a PEG ratio of 0.94. This figure is similar to the commonly-used P/E ratio, with the PEG ratio also factoring in a company's expected earnings growth rate. CI's PEG compares to its industry's average PEG of 1.14. Within the past year, CI's PEG has been as high as 1.09 and as low as 0.73, with a median of 0.92.Value investors also use the P/S ratio. The P/S ratio is is calculated as price divided by sales. This is a popular metric because sales are harder to manipulate on an income statement, so they are often considered a better performance indicator. CI has a P/S ratio of 0.49. This compares to its industry's average P/S of 1.09.Finally, our model also underscores that CI has a P/CF ratio of 7.37. This figure highlights a company's operating cash flow and can be used to find firms that are undervalued when considering their impressive cash outlook. CI's P/CF compares to its industry's average P/CF of 13.44. CI's P/CF has been as high as 9.76 and as low as 6.52, with a median of 7.74, all within the past year.These are only a few of the key metrics included in Cigna's strong Value grade, but they help show that the stock is likely undervalued right now. When factoring in the strength of its earnings outlook, CI looks like an impressive value stock at the moment.Want the latest recommendations from Zacks Investment Research? Today, you can download 7 Best Stocks for the Next 30 Days. Click to get this free report Cigna Corporation (CI): Free Stock Analysis Report To read this article on Zacks.com click here. Zacks Investment Research