Next time some one trash talks you start finding rocks along the course and add them to his bag one at a time. Of course you want rocks that are not too big but will add weight. By the end of the round his bag should weigh twice as much as it did when the round started.
We do this on caving trips, hiking trips and any other place we can possibly get away with doing it. We call it simply "Rocking" another person. It's usually done while someone is going down a side passage or checking a lead, we aren't subtle either, we try to add a pound at a time.
I got trash talked one time, told the guy if he didn't stop I was going to break every bone in his throwing hand. Shut him up and he left. Still threw my game off, I hate promising violence to some prick who is used to doing it while playing other sports. It's like punishing a dog for something it has always been rewarded for in the past.
That being said, I've never felt the need to do it, even in good fun. Easier to compliment and be generally happy for someone than be that competitive that I'd have to stoop to that level.