I've had a few in the far past, mostly motoring related
1. Welding new fillter nozzle onto a fuel tank. I'd flushed the tank out thoroughly with water a few times, but seems there were still fumes left so it went bang while I was welding. Fortunately not enough to cause any damage, except for my ears ringing for quite a while. Found out afterwards that tanks should be steam cleaned, not just flushed with water.
2. Cutting a car apart while scrapping it, using an angle grinder. The interior caught and the car went up in flames. Since a lot of the car was already out, the thing flared up and was out within the space of a minute.
3. Cleaning a car battery up - used a wire brush to clean the terminals. That caused a spark and as the battery had been on charge, there was presumably a build up of hydrogen. Another bang and the battery casing split, spraying a small amount of acid over my jeans, which then disintegrated around the splash marks over the nex few washes.
4. Car radiator sprang a leak, so I temporarily repaired it by blanking off a couple of the radiator fins. What I hadn't appreciated was that the radiator was pretty much on the limit of it's cooling capacity for the car (it was a kit car) so on the motorway, it couldn't cope, resulting in overheating on one piston, with damaged piston ring, melted piston crown and pretty the whole of the contents of the sump being burned off in the space of about 30 seconds. As well as the piston being partially melted, the shattered piston ring bounced around the cylinder leaving lots of little dents in the piston. Amazingly, no damage to the piston bore, so a new piston and new radiator and it was fine again. Still have the old piston as a paperweight on my desk.
Haven't really had any house related DIY disasters as I try to avoid doing DIY if I can.
I haven't had too many so will share my dads as he has LOADS!!!
Working on his car he was removing the engine to replace a noisy chain, the old Renault 5's had the chain on the back of the engine against the bulk head he was putting the engine back in, was almost done when he touched his metal watch strap on main live feed to the cars electrics, the strap was instantly soldered closed onto his wrist he had a very large burn that wouldn't heal for months, not helped by infection and irratation caused by the only fluid he could find to cool the burning quickly which was a bottle of brake fluid.
He was planing a door to fit with an electric plane, and cut through the cable, he was lucky not to hurt himself, so he shortened the cable which ended up being about 12 inches carried on, the plug got stuck so he looked down and put the plane (still running) straight over his hand taking out large chunks.
He was given a nice solid wooded front door so thought he would replace the old glass panelled one, built a new frame to fit the door, fitted it all in place onlt to then realise the door was too big for the opening so had to go and get a stone cutter to widen the doorway.
There are probably many more I have forgotten about but there's a few.
On a different not this is a true story of how a man lost his life in the US it's in the Darwin awards.
Chap was cleaning his motorbike and giving it a service, he had almost finished when it fell off the stand and crushed his leg, his wife called an ambulance and they took him to hospital, his wife cleaned up the mess whilst he was gone and then went to see collect him, he had his leg in plaster but no major injury, he went home was sitting on the loo whilst smoking finished the cigarette and put the end down the toilet, not knowing that his wife had poured the spilt petrol down there, the explosion knocked him off the loo. Ths wasn't what killed him though, it was actually the same ambulance drivers that came out to him and whilst laughing so much at how unlucky he had been, they dropped him going down some stone steps and he landed on his head and was killed.