We're all familiar with giving the finger, flipping the bird, the single-digit salute, and all of those other synonyms for the (American, at least) universal symbol of phallic aggressiveness which says in no uncertain terms, "Fuck you!"
But is this always the sentiment we want to convey?
A Rennie I worked with last year has a much more damning gesture she uses, only in situations of extreme duress with friends involved. This one takes a bit of practice. Hold up your hand, palm inward, such that all fingers but the middle finger are extended. (Doing this gracefully is what takes practice.) When the object of your ire boggles at you uncomprehendingly, declare venomously:
"Unfuck you! May you NEVER get laid again!"