Nanny, au pair, or babysitter: No need to tip. She's stealing your jewelry and having an affair with your husband.
Teacher: Do you want that dopey kid of yours to get into college, or do you want him sleeping on the futon in the basement for the next 10 years? $1,000 per A given.
Hair stylist: Want to look like Bozo? The price of a haircut. Want to look like a human being? Just open your wallet and let her dig in.
Garbageman: Nothing. He's going through your trash and selling the good stuff on eBay. That painting from your attic you threw away? It was a Pollock.
Fitness trainer: Everyone knows you're sleeping with him.
Housekeeper: Please--she's in cahoots with the au pair.
Pool boy: Up to you. Depends on how good he looks in a Speedo.
Yard worker: Isn't keeping his secret from the immigration authorities enough?
Boss: An extra brown-nosing session.
Mail carrier: Unleash the hounds!
(There's real tipping advice here if you need it--and I surely do.)
UPDATE: Bleh. Gawker used basically the same gag on Dec. 4.