Well, here's a few from me:
1. Built the Monogram Me-109 back in the mid-70's as a kid. Our small house had the central air vents high on the wall (close to the ceiling), and the register on one of those had come off. So, a large rectangular hole was left in the wall. It was winter time, so the heat was running. I decided that after hand-brush painting my 109 (who could afford an air compressor back then?), I would just stick it in the vent for a few minutes to dry that paint really quick. I left the right wing sticking partially out so I could handle it when I retrieved it. Well, about 10 minutes later, I looked up, and the right wing was now bent/warped downward at a 90 degree angle, and the rest of the plane wasn't looking so great, either. Didn't realize the heat got that hot........
2. A few years ago, I was building the Hasegawa F-16D (two-seater) with the gloss white & high-visibility orange markings for Nellis AFB. I decided I was gonna be really smart, and fill the nose cone with Squadron putty for nose weight instead of my usual lead shot and 5-minute epoxy. After I got the nose cone filled with putty and glued to front of the plane, I put it aside until the next day to give the super glue time to cure, so that when handling it, the nose wouldn't fall off. Imagine my surprise to find that, when the putty cured, it heated up enough to make the nose cone look as though someone had taken a 1/48th sledge hammer to it and just beat the crap out of it. Won't be doing that one again.
3. On Mother's Day 2012, I was replacing the boards (they were all warped from age) on the back deck at our house in Georgia. I had just finished cutting the last board on the table saw, and turned the saw off. While the blade was still slowing down, I saw a piece of scrap wood on the upper right corner of the table surface. I reached with my right hand to get it, heard a very loud "TANG!", and said to myself, "What the heck was that?" I looked around, didn't se anything obvious, then looked at my right hand, and saw that I had just turned my index, middle, and third fingers on that hand into something akin to pulled pork BBQ. Saw the bone in all three, and all three fingernails were gone. Never felt a thing. Stupid me had forgotten to put the blade guard down when I shut the saw off. Luckily, the ER doc at the hospital was able to save everything, and my right hand is 100% usable again. The middle finger only has the right half of it's fingernail, though. The story of the hospital visit for this is even funnier, and involves Facebook and a bunch of curiosity seekers, but I'll have to tell that one later