Here's an obnoxious one... I sold a guy a factory sealed blu-ray.
He comes back over two weeks later to say that there's a small tear in the cardboard on the slipcover and he'd like to return it.
From his photos it appears he's removed the shrinkwrap. So I ask him about that and offer a partial refund for the cardboard tear... no response.
I call eBay and ask what to do - they said that they expect me to provide a label and accept the return, full stop. So I'll spend money to ship it to him, pay for him to ship it back, and then end up with an item that isn't in the condition I sent it to him in and is worth less for having been opened.
1 out of 10.