My favorite is when a customer picks something out of a book that is special order, it shows a pic with all the dimensions. You order it in for them, they pick it up and over month later they want to return it because it is 50% too small for what they want.
You try to do your best in the name of "Customer Service" & take it back even though it's been over 30 days and it was special ordered, but you take it back anyways. Then the customer gets all bent because you charge them 25% for a restock charge....