My friend always says "Don't look at me in that tone of voice" - which pisses me off slightly because it doesn't make any sense.
Theres a lot of strange ones that everyone uses like "Clean as a Whistle" and "Mad as a box of frogs" which don't make sense because since when was a Whistle particularly clean?
I think the best phrase I have ever heard was from "Blackadder" which goes "I know from long experience that my men have all the artistic talent of a cluster of colourblind hedgehogs... in a bag." haha!