Today's WSJ has an official list of what are permitted and prohibited as carry-on items for airplanes. "Kubaton" is listed as one of the items, new to me. On Google, it's listed also as kutotan and kubatan. Looking at images does not convey the purpose of the kubotan. On the list also were "numchuck" (nunchaku) and "throwing star." But not Leatherman. Despite anecdotes, knitting needles and nailfiles are apparently permitted.