While the proven Zacks Rank places an emphasis on earnings estimates and estimate revisions to find strong stocks, we also know that investors tend to develop their own individual strategies. With this in mind, we are always looking at value, growth, and momentum trends to discover great companies.Of these, value investing is easily one of the most popular ways to find great stocks in any market environment. Value investors use tried-and-true metrics and fundamental analysis to find companies that they believe are undervalued at their current share price levels.Zacks has developed the innovative Style Scores system to highlight stocks with specific traits. For example, value investors will be interested in stocks with great grades in the "Value" category. When paired with a high Zacks Rank, "A" grades in the Value category are among the strongest value stocks on the market today.One stock to keep an eye on is Plains All American Pipeline (PAA). PAA is currently holding a Zacks Rank of #1 (Strong Buy) and a Value grade of A. The stock holds a P/E ratio of 7.22, while its industry has an average P/E of 9.38. Over the past 52 weeks, PAA's Forward P/E has been as high as 824.86 and as low as -1,948.89, with a median of 7.64.We should also highlight that PAA has a P/B ratio of 0.93. The P/B is a method of comparing a stock's market value to its book value, which is defined as total assets minus total liabilities. PAA's current P/B looks attractive when compared to its industry's average P/B of 1.30. Over the past 12 months, PAA's P/B has been as high as 1.14 and as low as 0.53, with a median of 0.84.Finally, investors will want to recognize that PAA has a P/CF ratio of 5.39. This metric focuses on a firm's operating cash flow and is often used to find stocks that are undervalued based on the strength of their cash outlook. PAA's current P/CF looks attractive when compared to its industry's average P/CF of 6.07. Over the past year, PAA's P/CF has been as high as 13.21 and as low as 3.27, with a median of 5.78.These are just a handful of the figures considered in Plains All American Pipeline's great Value grade. Still, they help show that the stock is likely being undervalued at the moment. Add this to the strength of its earnings outlook, and we can clearly see that PAA is an impressive value stock right now. Zacks' Top Picks to Cash in on Artificial Intelligence In 2021, this world-changing technology is projected to generate $327.5 billion in revenue. Now Shark Tank star and billionaire investor Mark Cuban says AI will create "the world's first trillionaires." Zacks' urgent special report reveals 3 AI picks investors need to know about today.See 3 Artificial Intelligence Stocks With Extreme Upside Potential>>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 Plains All American Pipeline, L.P. (PAA): Free Stock Analysis Report To read this article on Zacks.com click here. Zacks Investment Research