The Reuleaux Triangle, named after Franz Reuleaux, is this odd roundy triangle, which would hardly seem worth naming after someone, except for one unusual feature: However you turn it, one side is always the same distance from the opposite side. If you were to put a board on a couple of Reuleaux Triangles, it would have a perfectly smooth ride rolling on them. So what you say? A circle does the same thing? You know how whatever shape drill you use, the holes always come out round? A Reuleaux drill can drill square holes. Not even Chuck Norris can do that.
There are three dimensional equivalents as well:
These shapes of constant width have other uses besides looking funny and drilling square holes. Any time you invent a different way for machines to translate one type of motion into another, you have great potential for new inventions. I suspect this one is under-utilized.