Dropped $300 on a thermal camera for my phone and it's the best tool I've bought in a decade
I was on the fence for a long time, thinking it was just a fancy gadget. Then I got a call for a fridge that was running but not cooling right. The usual checks showed nothing. I hooked up the camera and in two minutes, I saw a cold spot on the evaporator coil that pointed to a partial blockage. Without it, I would have been guessing for an hour, maybe ordering the wrong part. It paid for itself on that one job alone. Now I use it on every appliance to spot hot connections, bad elements, and airflow issues. It cuts my diagnosis time in half. What's one tool you bought that you now can't work without?