What's your favorite tool that is best known for it's use in another trade?
For example, my favorite non-electricians tool is the C-grip which is usually used by welders. It uses the vise grip action but instead of a pleirs end, it forms a big C. They're great for holding a panelboard in place while you reach for the screws & your cordless screwdriver. Also handy for holding conduit to beams & girts while you dig around for a strap. I refer to my pair as my third hand.
Few things are harder to put up with than the annoyance of a good example.