I think someone may have already mentioned one, but since I used it another half-dozen times over the last week, I'm calling out my Bosch StarlockMax oscillating tool. I was mostly doing interior carpentry back when I bought it, so I got the highest-power corded option they had at the time. But lately I seem to be using it outdoors more and more, and wish I had a cordless version. Might have to buy another one.
Somehow I made it through nearly 40 years of life before realizing how damn useful this tool is, for all of those jobs that require a lot of time and elbow grease. It's most useful for undercutting door casings when changing flooring thickness, but this weekend's job was carefully plunging into several buried PVC conduits, believing I had identified which of the bunch were unused versus containing wiring, but never quite sure until you cut. With the Osc, you can carefully scarf out a window and peak inside, before commiting yourself. Since I already had it out in the yard, I also used it for cutting a bunch of drain pipe and even PVC conduit, and found it does a nice clean job of that. Better and easier than the classic hack saw or recip saw.
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