I once heard the late George Carlin at a live performance reel off hundreds of witty slang synonyms for masturbation, but his final entry, and the punchline for his entire performance, was,
"Crowning the King."
I thought it was the funniest.
Queen Elizabeth II: Prince Andrew! Prince Andrew! How much longer are you going to be in there?
Prince Andrew: Just a little while longer, Grand Mum.
Queen Elizabeth II: Prince Andrew! You are not endevouring to masturbate in there, are you?
Prince Andrew: Of course not, Grand Mum--I'm Crowning the King!