I know someone posted a link to one of the 'Darwin Awards' given to people that have died in ridiculous circumstances at the start of this thread, but I own one of those books, and here are my 3 favourites. (All are true, I'll find the book and scan in the page if needs be!)
1. One man (in America I think?) stole a vintage WW2 pistol from an old mans house, tried to hold up the local cash and carry. When the cashier refused to hand over the money, CCTV images record the criminal pulling the trigger. Noting immediately happened, so the criminal is seen to turn the gun to his face to look down the barrel. Because the vintage pistol contained vintage ammo, there was a delay in ignition. Long story short, he shot himself in the head!
2. There was a court appearance with a man charged with possession of a live hand grenade which had a 5-metre kill radius. The defendant avidly protested it was fake. Apparently, as the case drew on, the Judge got bored and pulled the pin out of the grenade.
3. And a final quick one- A bloke was pruning a tree, and cut off the branch that he was sitting on - fell to his death.
Hopefully these are useful!