I think mine would have to be when I scorched a baby wipe. I had saved a baby wipe that I had used to wipe up ink. I tried to emboss on it so that I could use the wipe on a card (in place of paper/fabric). While I was using the heat gun, the wipe started smoking. It was seconds from catching fire, and it threw a good scare into me. I'm really careful now when I emboss, and I don't try to emboss baby wipes anymore.