I keep a large nut and bolt on my desk, and do them up and undo them when the urge takes me. They're well finished, with rough bits and smooth bits to touch.

Outside of work I rarely need anything like that.

Balisong or "butterfly" knife. Its got risk, flow, and steez all in one. Not super socially acceptable to use in public though

A "Rubik's" cube (actually a Chinese MoYu speedcube) that I tuned to feel "just right".

It's both a great fidget toy and a nice way to kill a minute or two with a puzzle when my mind drifts. I work from home and I find long meetings become much more bearable by just spinning layers at random or spinning it by its vertices.

The lightbulb moment for fidgets was my wedding rings and I guess my iron ring. I got my iron ring a few years before I got married and I was always tapping it on hard surfaces when I was thinking but part of the whole thing is that it's supposed to remind you of your obligations as an engineer so I thought that was normal?

I would constantly tap my wedding rings with my thumbs of the same hand and joke that they give me my strength. My partner is my rock but the secret sauce is the stim lol.

I think your actual question is about what purpose built fidget toys we like? My current fave is something like this:

It's hard enough being a 40+ lady type whose job it is to argue on construction sites without bursting jell filled stress balls all over yourself lol. I like that this one will not explode. I honestly dgaf that it's 'childlike', I'd love to have someone make a shitty remark to my face. I've got the "say the vilest shit imaginable impulsively" autism.

A heavy pen to roll around on my hand and between my fingers. Even when I'm working on a computer, i got my trusty pen within reach.

I will take sweatshirt strings, pull them out, and tie knots along the entire length of the string. I then take and roll those knots in my fingers. I could probably use a worry stone, but something about about rolling the hard knots between my fingers seems to suit me better.

Probably gonna sound weird. But I have a bunch of textured beads on a bracelet. The textures vary enough for me that i can spin them or pinch them between my fingers and it doesn't "look" like a fidget so I don't get a lot of weird looks. I have also tried knotted bracelets and those are good too but they aren't as easy to clean and texture of the material could be a problem for some.

I have the prickly stim ring and the prickly roller those are my favorites

I really like my Ono Roller! I keep misplacing it tho lol

For me any soft foam ball I can throw at the wall and then catch again. It's occupying brain regions I don't need for reading or watching on the monitor while not making noises for my neighbours.

A baseball to do pitching grips

My partner got me a fidget spinner ring and now I’m permanently fidgeting.

I got a lot of fiddling with things when I was a kid so all my fidget toys that I found for myself got taken away in the places I needed them most like school etc. My solution was to use my own hands. I curl my fingers a little and then touch the crease between the first and second metacarpal on the index finger, then go down to middle and ring in the same spot, then diagonal up to the flat of the second metacarpal then the crease of the second and third metacarpal, then I reverse course. I can do the same with the straight from the second to third metacarpal crease on index, middle, then ring, then diagonal up to the first to second crease on the index. It is a nice pattern and except for times where I have broken or flayed my hands respectively it is always available. I can go slow or fast, do variations of the patterns, and I can do it subtly so people don't notice. Very... Handy. Ha.