I am an evil gamemaster.
I once had a player whose character always demanded some sort of proof that his new-bought magic item would do what it was supposed to do.
Seems I'd screwed him over a couple of times with dishonest shop keepers or something.
So he demanded proof that his super sharp sword would actually close the deal.
So the merchant chopped an anvil in half for him.
HUZZAH! He proclaimed and purchased the sword.
Did I mention that he never paid more than 10% of the market value for anything? The GM was screwing him because he was haggling in an insulting manner to the merchants.
Well "Anvil Slayer" was all that sword did. But he got a GREAT deal.