I have very fond memories of one episode in particular where they encounter this guy that has a persuasive ability. he can make anyone do anything that he wants. In the very first part of it he tells Dean "hey man, nice car! Can i have it?" and Dean gives it to him.

I can't remember how they would possibly pull one over on a guy that has the superpower to make anyone do whatever he wants but as usual, the Winchesters pulled it off!