This one hasn’t been mentioned: I chew on my fingertips. Not fingernails (although I do that too), but the patches of skin on either side of the nail. The weird thing is I’m supersanitary, but I stick the most germ-infested part of my anatomy in my mouth on a regular basis.
Oh there’s another one I forgot to mention that I didn’t think about till I got to work a few minute ago. I can’t stand to sit with my back either facing a door or a crowd. It really bugs me to have people milling about behind me. Sitting in classrooms was the worst if I got stuck in the front row for some reason, whenever someone behind me would answer a question or start talking to the teacher it drove me crazy not being able to see them (so I spent a lot of time twisting in my seat and craning my neck) In college I always sat as far back as possible, preferrably with my back to the wall, which surprised a few professors since I actually participated in class discussions a great deal, which I guess is unusual for the typical back-row dweller.