I got one.
A couple of months ago a young fellow walks into my shop with a S&W M&P 9mm in a pistol rug. He says he needs help, there's a live round stuck in the chamber. Nothing over-the-top weird so far. Then he says the round is BACKWARDS. He managed to load - don't ask me how - an entire magazine with the rounds pointing BACKWARDS and he properly jammed the first one into the chamber. Before I went into the back to clear his chamber, I mentioned to him that I expected him to pay whatever amount I said and with a smile on his face since I don't relish the thought of smacking a case head with a live primer. Center-drilled a brass rod and cleared his chamber. I gave him his pistol back and he paid as instructed. I reminded him that the pointy ends go forward.
A similar event happened to me while running a group of officers through annual re-qualification. The officer had loaded the entire mag, bullets backwards. When the slide didn't go into battery, he raised his hand for assistance, I explained to him that I just saved his life, and that had he pressed the trigger, he would have shot himself in the face. I cleared the pistol, and continued with the drill. (never told the guy any different).

Lloyd