Interesting thread! I imagine what works and what doesn't has a lot to do with geography and food sources in the water we fish. I've caught fish on most of the flies folks have found unproductive. I've done very well with scuds in olives, tans, chartreuse, pink, and orange in water where scuds live. I've also done well with copper johns in various colors especially when fished in swifter pocket water found in Western Freestone rivers where you need to get the fly down quickly. My most productive fly is a Microbugger in olive or black and in size 14 or 16. I fish it dead drift as a nymph and stripped as a streamer at the end of the drift.

Now a fly I've done poorly with is the Silver Hilton used for steelhead. I know steelheaders who swear by it, but it has never been productive for me so it just sits in the box while other, more productive patterns see a lot of water.