Conversation: When your lovely lady talks about a very collectable item (ie a book, LOTR figures, etc.) that she is looking for or would want, mention that you saw several of them at Goodwill the previous week, and decided against buying them. Then innocently ask, "Should I get them the next time I see them?" The true reality of the situation is that they will never show up at Goodwill.
Personal Outcome: This one is so old that acceptance is not possible. However, it is still good for a chuckle, and lovely lady still sighs at my fun-filled attempt at humor. WARNING. This one is very powerful, probably setting you up for being called an asshole.