I bounce my legs too, sometimes. It just feels nice.
I also twitch my head to one side (usually the left) from time to time, which acts as a sort of "reset button" for whenever I'm thinking unpleasant or painful thoughts (try it, it really works!
). If I'm not careful, though, it can develop into a prolonged twitching session which I have to try very hard to stop.
My most common stim, when I find something to open and close (DVD & spectacle cases, fold-out car-keys, bottle caps), is something I do consciously when I have to stop myself from really fidgeting - if I'm playing with something in my hands then I don't have to move around all over the place. I remember I used to run around the room when I was watching Tom & Jerry cartoons as a little boy - I wonder if I would have sat still had I had something to keep my attention? I still get the urge to run around now, but I can manage to resist it these days 
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Why so serious?