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.

Of these, value investing is easily one of the most popular ways to find great stocks in any market environment. 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.

Vista Oil & Gas (VIST Quick QuoteVIST - Free Report) is a stock many investors are watching right now. VIST is currently sporting a Zacks Rank of #1 (Strong Buy) and an A for Value. The stock is trading with a P/E ratio of 3.55, which compares to its industry's average of 7.38. Over the last 12 months, VIST's Forward P/E has been as high as 20.44 and as low as 2.83, with a median of 4.04.

Finally, we should also recognize that VIST has a P/CF ratio of 3.16. This metric takes into account a company's operating cash flow and can be used to find stocks that are undervalued based on their solid cash outlook. This company's current P/CF looks solid when compared to its industry's average P/CF of 5.79. Over the past year, VIST's P/CF has been as high as 3.65 and as low as 1.63, with a median of 2.71.

Investors could also keep in mind YPF Sociedad Anonima (YPF Quick QuoteYPF - Free Report) , an Oil and Gas - Integrated - International stock with a Zacks Rank of # 2 (Buy) and Value grade of A.

YPF Sociedad Anonima sports a P/B ratio of 0.31 as well; this compares to its industry's price-to-book ratio of 1.61. In the past 52 weeks, YPF's P/B has been as high as 0.32, as low as 0.11, with a median of 0.20.

These figures are just a handful of the metrics value investors tend to look at, but they help show that Vista Oil & Gas and YPF Sociedad Anonima are likely being undervalued right now. Considering this, as well as the strength of its earnings outlook, VIST and YPF feels like a great value stock at the moment.