It turns out to be fairly easy to find things around the house that are round and sharp.
There's my old hunting knife, bought decades ago when I started camping and never used to gut an animal or skin out a deer. The end of the blade is round, but it is still sharp, despite a few rust spots from all those years of laying in the toolbox in the garage. And the point can still stab into wood and the surface can reflect a round note, in this case a D, that is also sharp.
But I also like the round grip, made from stacked pieces of leather. Don't know why. I just do.
And finally, even in the kitchen, round sharp things abound, especially from Pampered Chef. There's the pizza cutter, the apple corer/sectioner, and perhaps my favorite, the pineapple peeler/corer/sectioner. All are so sharp they need plastic covers, but that pineapple thing on the right will take your finger off if you aren't careful. We've had to rinse the blood off a couple of pineapples. But it works GREAT!