Roscoe writes: “This handy little tool is the size of a screwdriver and has a tip with drill flutes, but the body has very sharp spiral saw teeth all the way around. I just got one as an early Christmas present and am looking forward to using it. It looks to be just the thing for adding electric boxes in a remodel.”
Indeed! This looks a lot like a large version of the “side-cutting” bits used with rotary tools. The pictured model comes from Craftsman/Sears and runs $8.
Craftsman 8″ Drill Saw [Sears]