Early(ish) in my Grandma and Grandpa's marriage, my Grandma had asked my Grandpa what he wanted for Christmas.
His reply to her? A Left Handed Monkey Wrench.
She evidently went to several hardware stores all over Portland, Oregon and had no luck finding one. At last she discovered why. At one store she asked a sales person if they carried them. This person was kind enough to let Grandma know that she'd been had. There is no such thing as a left handed monkey wrench.
Knowing my Grandma, and her various responses to my Grandpa's antics, I would have LOVED to have seen what she did to get him back. Unfortunately she would never tell us.
I do know that she most likely received an apology for it. Whenever Grandpa did something like this or something to make her angry, with his apology he would give my Grandma a very nice gift. As her house was full of very nice things, I suspect Grandpa was quite a bit more of the practical joker than we all knew him to be.