At 52 I started to floss my teeth, (better late than never), I bought various items for to see which ones could work better for me.
One of them is a dental floss holder, (by Gum), which I don't like very much for flossing, (I like more Ultraclean by Listerine for flossing molars), but I discovered that it is a good rattleback. I try to spin whatever object happens in my hands, and this one was a surprise, I never saw a rattleback before.
It works only when spun in one direction.
https://www.youtube.com/watch?v=NdXrWKmWC94