Okay, here's mine, plus some bonus tales...
My friend had just stopped by the house to show me his new Winchester Defender 12 ga. He pulls up in the drive way, and gets out his new toy. I watched him unload the magazine, so I know it's unloaded, right? Well, he hands it to me, I look it over and try to work the action. Doesn't work. Now, being used to older shotguns, that doesn't rattle me. Not thinking to look for the release, I pull the trigger, knowing that will release the action. BOOOOM! The Defender jumps out of my hand, gets scratched on the gravel drive. Leaves from the hickory tree are floating down (fortunately, I had a dad that taught me about always pointing in a safe direction), my friend is yelling "what the hell are you doing?" and my ears are ringing. I missed the bug zapper by about a foot.
Later, the same friend decided it would be a good idea to unload his .45 since he & a friend were drinking after work. He nearly shot another friend of mine when his thumb slipped off of the hammer. We dug the slug out of the floor so he could have a little reminder....
Another - normally very safe - friend of mine was cleaning his FN-FAL in the kitchen and left a round in the chamber. BOOM! His wife comes running, and there's water shooting out of a hole in the kitchen floor. It seems he managed to hit the main water line...
Last, but not least, the king daddy of all stupid discharges....
An acquaintance of mine - someone I had been shooting with, but wouldn't go again before this incident - had a Desert Eagle .44 mag. His story is he was walking along with the pistol on his shoulder when he saw a snake. It made him jump, the pistol went off. Yes, he shot himself in the back, leaving him with a funnel shaped powder burn on his back and a chunk missing from his butt. So, if this is the way it happened, he was walking with a loaded pistol on his shoulder, safety off, finger on the trigger.
Now, as monumentally stupid as that seems, a friend of mine came up with another thought. You see, he was a member of the same range as this turkey, and had seen him using the front site of his Mini-14 for a back scratcher...
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Beginner barbarians probably had the idea that every house they broke into would be full of untouched loot and frightened, unarmed victims. It just doesn't work that way, my friend.