Rick's Boa Yarn Leech is a great fly especially for still waters when you want to swim a fly very slowly and have it sink very little. Short jerky strips during the retrieve give the fly great action in the water.
Fish love it! For example, here's what happened last night:
I was using a light gray-colored boa yarn leech, and a small bass hit the fly. It broke the tippet at the knot on the hookset, mostly because the line had gotten worn and damaged from use. The fish was probably 30' away when it hit, but after the line broke it jumped out of the water so I did get to see it. Anway, so I tied on a yellow Boa Yarn Leech next and continued fishing. About 10 minutes later, I caught the bass that had broken my line. The two flies were right next to each other in the fish's mouth. I was glad to get my fly back!