When sitting I kind of bounce my right knee up and down, people either don't notice at all or are driven insane by it. Most decisive.
If I've let my scraggly-ass chin whiskers grow out then I'll tug/twirl them.
I also fiddle with anything I have near me...and smell it. Really.
Hand me a 360 controller? I'll smell the plug-area on the top of it.
Took my glasses out of their case? I'll smell the interior of the case.
Just used a lighter? I'll smell the burned metal-bits on the top.
Don't have anything? I'll make my hand into a very loose fist and smell the inside of it.
...
Yes, I know that's fucking weird. I don't really even notice that I'm doing it either, my friends have to tell me later on that I was being nutty.