Subject: Re: Violent Gestures
That's actually been around quite a while and (I think) across sports, both amateur and pro. If I'm not mistaken, it began with a gesture of slitting someone's throat.

I definitely agree about the celebratory dances/jigs/idiocy. I recall a story about Bear Bryant witnessing such an act and telling a player who'd just rushed for a TD, "Son, act like you've done it before."