The other day where my wife works someone called in after eating at her restaurant two weeks ago. It was another server but anyway the lady says she thinks she overtipped $10 and would like that amount back in the form of a gift card.
The waiter had to buy her a gift card for $10. Out of her pocket of course!
So if you are need of some money just call your local restaurant where you last ate and ask for some money back because you overtipped.