I'll say, in my horrible Indian-style voice - "Please for you to go **** yourself hard, goodbye!"
My wife will say "hold on" and walk away from her phone. She also has a great voice, imitating a three-year-old, and she'll say something like "Mommy can't talk now. Mommy and Daddy are *******. Bye-bye!" Or, she has a LOUD referee whistle that shuts the telepunk down, too.
We've done the sex-noise tactic, complete with my dog howling on cue. I've wondered what the person on the end of the line is picturing in their mind - me and my wife in a three-way with the dog, or me humping the dog furiously! Either way, we laugh our asses off about it!
My favorite is "Dammit, Bobby, where are you? Did you get the hole dug?" Usually, silence follows...!