At Quest Martial Arts in Ann Arbor, we teach a variety of weapons as part of our Leadership program. One of the more practical and versatile weapons is the kubotan. Traditionally consisting of a hardened metal rod, typically about 5 and a half inches and slightly bigger around than a pen. It can be held in one hand with the ends sticking out either side of the fist and can be used to strike bones or kyushu (pain points). We even have a keychain version available in our Pro Shop!
Image source: https://upload.wikimedia.org/wikipedia/commons/d/d0/Ku2.JPG