now we all know we all work on our cars a lot. What's the biggest fuckup you've made?

Mine would be not disconnecting my battery when I went to change out some oil feed fittings on my car, thinking that since I was doing absolutely nothing electrical related it would be no big deal. Unfortunately, something was grounded and I seem to have found an exposed power point as well (probably one of the connections on the starter) so that when I rested my turbo on that ledge, and touched my SS braided feed line to my charge pipe, the whole SS line caught fire and started smoking something fierce. I managed to disconnect the battery before it reached any fuel lines (which as you can see are quite close to the oil line, one of the things I did is relocate it across the engine bay to the normal spot though).
I've always been of the school of thought that "if it doesn't catch fire, no big deal" but obviously anything in my car could catch fire at any moment. The line sprouted a bunch of crispy white fuzz, is torched black in some parts, and no longer lets anything through. Only $50cdn and now at least I can get one thats the right length, but it also melted the wires going to that EGR valve, so I get to remove that now too

1995 Eagle Talon ESi