Now here's a great post. I usually only shit talk when somebody dishes it at me. Can't think of any good ones at the moment. I have been known to say "Hey put some Viagra on that thing" when the putt goes low.
I like to constantly remind someone of their obvious screw-ups in a very simple manner.
Example: Someone hits a tree and I turn to them and say "your shot just hit a tree." Someone tries to lay up for a safe putt and ends up short, I say "Your lay up was short." Someone throws a worm-burner, and I say "your drive was too low."
It's a very simple and effective way to throw someone's game off. Instead of focusing on their shots, they will be more focused on the annoying crap I'm about to say. It's not very witty or edgy, but with repetition and good timing, it will drive them #@$%ing crazy!