What’s the tool you bought and never use but saves your butt when you do need it?

BKCowGod said
My '73 Land Rover has a hand crank starter option. Alternator went out and I accidentally turned it off in the parking lot (Diesel). Got a lot of weird looks using that one, but it got me home!

not in my toolbox, but a mig welder , and a lathe ----