The "I wanted/need this so bad for my car" routine and then you see it up for sale the next week at 2x+ your selling price. Happens often. Just have to be happy with your selling price and move and... just remember who pulls that stuff in case they ever call again. :)
The other for me is holding parts for people then seeing them out buying parts with money they should send you to finish a deal. Especially irritating when they buy something that you really need. Hard enough to find some stuff, even harder when the others are buying with money they should be sending you. LOL