My guys (especially my 1.5yo male) wag their tails just before they attack - the dog, the cat, each other. It's especially funny to watch when the tail is all you can see, ie, the rest of their body is under the couch, a blanket, etc. It makes you take notice and watch because you know something is about to happen! They also tail-wag when they are playing in their tube. [Posted in FML issue 2376]