Post 'em here folks, help me out.
I have one or two:
"pooh" -- in the outside world, this would be considered the "perfect" sign. index finger & thumb touch tip to tip, fingers 3 4 5 extended. "pooh" meant "I agree", as in "oh, pooh!"
aim your eyes in the right direction -- move hand in "pointing" formation: put index finger at corner of eye, then move the hand to point in the direction of the person speaking, or whatever it is we were supposed to be paying attention to.
pay attention, or wake up -- curl fingers so the tip of all the fingers are touching the tip of the thumb. then flick the hand open so all digits are spread out. This gesture is done at someone's face to tell them to wake up or to pay attention.
I would be interested too in communication that was outside the rules. I specifically remember being in the bathroom with two or three misbehavers and they were totally just talking to each other. I can't think what the context was, maybe I was on T&R.