Back when I worked at the medical clinic, I got pretty good with the exam room tools. I could spin a rubber reflex hammer around one finger, and I got fairly adept with rolling an otoscope in my hand. If you could get the nervous children laughing, it made the exam easier for everybody: "Let me look in your ear ... my, what is that? Is that an elephant in your ear?"
The otoscope, a device for examining ear canals, used a rechargeable battery and was of knurled stainless steel, had a barrel about six inches long, and was a little slimmer than a D-cell battery in diameter.
I always thought that cylindrical shape would make a great knife handle, for a couple of reasons–first, it was heavy, and the butt could be used as a striking weapon. The shape and heft allowed it to be manipulated easily, rolling, spinning it from ice pick to saber would make it fun to play with, even though once you had serious need of a knife, you wouldn't be changing your grip.
I'm not sure of the best method of construction. Could be full-tang, with hardwood scales sanded to the round shape. Or maybe a metal tube with the tang set in a handle full of epoxy or some such, and a small tsuba-style guard. Drop-point, sharped one edge, maybe a false edge on the spine over the point. It would only work if the handle was longer and heavier–4.5 inches or so, with a 3.5 inch blade.
Probably just a blade-cover Kydex sheath; leather that would hold that shape usefully on a belt, might not be easy, but what do I know?