I thought about putting this in petty accomplishments, but sometimes I think about this thrad and how it exists to make it look like I only learned 2 things in the last 2 years, so ... BAMP!
I learned to solve a Rubik's Cube!
I don't remember exactly how long ago I started, but I could do it when I was at my friend's house for New Years, so I must have learned it last year sometime. I took my cube with me, and her kids had a couple cubes as well, so anytime I saw one laying around unsolved, I would solve it, and whenever they saw a solved one laying around, they would scramble it. Who knew kids were good for something?
Since that time, I have learned how to do the first 2 layers at the same time, intuitive-F2L-style, but I still have to use beginner methods to solve the last layer, so I haven't bothered to start timing myself. But I am constantly playing with it, and getting better at recognizing the different states and discovering my own shortcuts, so it's been a real slow and satisfying burn to get to where I am now, and I still have tons of room to improve.
As far as fidget devices go, it is endlessly entertaining. If I just need to fidget, I can flip and twist and turn and scramble that shit all day. Then if I need to focus my mind a little bit more, fuckin solve that bitch. It only takes a minute or two (I guess).