Not sure if this beats it, but...
I've got one customer that emails me periodically with "something". Most often it's something along the lines of, 'This other software that has a different purpose than yours does can do X. Why doesn't your software do X? Please put it in. And make sure there are no bugs. Other companies make software with bugs.'
Well, one of the first emails from him a while after he'd bought my software was that he couldn't open an audio file with it. Seemed strange to me, but after somewhere between 15~20 emails later I finally figure out that he HAS NOT INSTALLED IT YET!
Whenever I get an email from him, I just start laughing before I even open it, anticipating something that's just off-the-wall. He never fails to disappoint. And while I'm quite sure most developers would refund his money and tell him to go away (that has happened to him before), I think he's well intentioned, but just, well, whatever. He gives me a laugh.