I learned about the diamond plate, but it was just a tiny spark.
My biggest blunder was when I had a socket wrench that i was using to install 2 new 12v batteries on my trailer. The wrench slipped from my fingers and i accidentally dropped the socket wrench across the contacts of one of my new batteries when tightening a cable.
Luckily I had a shovle close by I could use to knock the wrench loose with which was now welded to the lugs. I used a rag to pick the wrench up to look at and man was it hot. Had to drop it and let it lay a while. The there was a melted spot on the handle and I was no longer able to operate the thumb lever to change the direction of the gears. Went back to the autoparts store for another battery.
That was about a 100 dollar accident. Now I slip a piece of hose over a wrench when playing with batteries.