I had a good one back in 2020.
I'd just decided to drag my old Jag XJ40 out of the bushes to rearrange things. I'd managed to overheat it and blow the headgasket a while back when I left it running and a coolant hose split, but it still drove itself up into position so it might drive out under its own steam.
Hook up a new battery and it turns over but doesn't fire. It's got spark so it's probably a fuel issue. Pull a fuel hose off the front and it's pumping water (the Jag's one major design flaw is a horizontal filler neck which allows water ingress if the drain gets silted up). The tank drain plug is pretty inaccessible, so I figured I'd take the level sender out so I could syphon the tank.
Of course, as soon as it's open water starts bucketing out of the tank and filling up the boot. I don't remember it being that full, so it must have got a lot of water inside it while standing. I know, I'll drill a drain hole to let the water out. Simple.
I go grab a drill, jump in the boot that's rapidly filling up and drill a hole. The second before I stop drilling the thought passes through my head of 'huh, I wonder how much fuel there actually was in the tank'. Stop the drill. Big fat spark and WHOOF! Turns out there was still about 20l of fuel in the tank, and I hadn't noticed the transition from water coming out to fuel.
I jump out, luckily not having been coated in petrol myself from the puddle I was crouched over. Promptly panic and freeze as there's a 10ft pillar of flame coming from the boot of the Jag. My mate who was working in the garage next to it pokes his head out and calmly goes to get a fire extinguisher. I pull myself together and rush to grab another one (lucky as we needed both to put it out).
Fringe was saved as I was wearing a beanie, no eyebrows, burnt lips, cheeks and nose but not too bad, and a boot that looked like this even after it was cleaned (turns out extinguisher powder is fairly caustic):
The Jag (and my face) is all fixed now, but that was definitely not my finest hour...