Segmented Pain Roller

It relieves anxiety for my wife to press her fingertips into something spiky.
She likes the Pain Roller by ItsMaitake.
https://www.thingiverse.com/thing:6820701

This is a similar concept but segmented to make it also a fidget toy and easier to fit a key chain into.

You can print as many segments as you like and they snap together.
No supports required.
I do recommend using a brim as the interior crescent snap collar doesn't have a lot of surface area on the first layer.