Tank top are something that I have learned to look for. They are great for layering under long sleeve shirts, layering under t-shirts, wearing them by themselves, or over a swim suit. But, I had the tendency to overlook them when I was garage saleing.
Because tanks are plain, a lot of times they are cheaper. If the person is selling t-shirts for $0.50, the tanks might be $0.25. Take advantage of tank tops and camis.