I used to spin pens around my fingers. Nowadays, without wanting to bring in my special interest again, I find myself almost involuntarily doing hand movements from my martial arts training (mostly parts of the Wing Chung forms, for anyone familiar with it).
I don't have a single toy left intact from my childhood for this exact same reason. Still do today, I always have parts of...things in my pockets, my current favourites are a titanium spork and the remains of a dynamo that I rigged to power a few led's and resistors. I feel really anxious if I'm not fiddling with something.