I did the SKS one, too. It seemed like the whole spring/bolt/carrier assembly was coming straight for my crotch. As fate would have it, I had good reflexes that day, and I jumped just enough when it came apart that the whole thing hit me in the solar plexus.
USP9 magazines. They just look like they don't need that weird plastic piece that holds them together from the inside. The tabs on the side *should* be tight enough to keep the floorplate on. Wrong! Floorplate, spring, and follower come shooting out the bottom of the mag hard enough to break a glass sitting on the table.
This is the best one. I hope I'm not the first to pull this. While disassembling a 1911, it did not occur to me that disassembly is usually the exact opposite of assembly. First thing I do is yank the retaining pin, and watch as the slide in all its glory, flies across the room and narrowly misses someone's head. *whew*