As I mentioned in another thread, someone grabbing my headrest. I am so fed up with that that I will loudly and aggressively confront people who are mindless enough to do it.

As a parent of a small child, I am acutely aware of his behaviour while flying. If he starts kicking the chair in front of him, he gets a stern warning and either my wife or I will lean over and apologize to the person in front. There is NO excuse for that kind of crap on a flight.