Reader Lesley threw these my way. They’re felt pebbles, going for as little as US$14 each. There are six different ones, and are “useful as simple decorative objects (a collection of them looks great in a bowl) or when used as a pincushion, etc.”
So they’re not entirely useless, and are only slightly less useful than real pebbles because you can’t use them as paper weights. In fact, if you buy them, you’d be supporting local craftswomen in Johannesburg.
And if you flung these at people, they won’t hurt a bit. Unless of course you were using them as pincushions. Or if you flung the bowl with them.