Wow, what a great thread, this is like Freak Confession. I have to contribute.
My only weird eating habit is that, unless I’m -really- thirsty, eating very dry food, etc, I always save my drink, all of it, until I’m done eating.
If I’m not wearing shoes, I walk on the balls of my feet. Heel never touches the floor. I tend to half-bounce and semi-sprint around, too…it’s impossible for me to walk normally unless I have shoes on. I feel weird running, like it’s “not right” if I have shoes on or not. I think my body wants to be quadruped 
I’d rather walk in grass next to the sidewalk, than on the sidewalk. This is less compulsive, though, since I feel rude walking in places with worn-down sickly grass that can’t handle the traffic.
I have this constant, irresistable urge to chew, nibble, gnaw, or just drool on something…lip, cheek, shirt collar, pen, cup, anything. It’s especially bad if I’m thinking about something at the time, particularly anything technical. If my brain’s going, I have to have something in my mouth.
I can’t sleep without weight on my chest. The only time I can sleep in any position but on my stomach, is while snuggling with someone else providing said weight. Speaking of weird sleeping habits, I too must have a blanket or sheet covering me at least from lower back to thighs, and that little only when it’s really hot.
My joints must be popped/cracked, or they feel stiff. Fingers, neck, lower back and ankles, in order of frequency and priority. It really freaks some people out that my back and neck can be popped, audibly, and not only does it not hurt, but feels better 
I can’t sit upright, in anything, I must slouch on my tailbone, with legs either stretched, or preferably tucked up. This makes me feel vaguely weird in a car, while playing flight sims with my rudder pedals, etc, where I -have- to sit upright. The only exception to this: to contently sit upright, I must have my legs tucked under me (cross-legged, yoga, whichever)
I also do the “Ow!” thing when bonking into anything that makes a noise, if it hurts or not. I know where this habit came from, it was cultivated by my parents. If I bonked into something enough to make a decent noise, I would get griped at – UNLESS I got hurt in the process. Eventually the “Ow!” became self-defense reflex, and used often since bouncing around on the balls of your feet makes for frequent collisions with doorframes, furniture, wall corners, etc. I’m used to it 
And now for my TMI: I hate body hair. Head hair, I love – I’m quite content with my “mane”, which lives pulled back in a ponytail past my shoulder blades. Eyebrows I can live with. ALL other body hair bugs me - arm, leg, facial, chest, pubic, whatever – I hate it! I think it’s ugly and uncomfortable. If I could wave a magic wand and be rid of it forever, once and for all, I would gladly do so.
Oh, and I talk to myself. Constantly. I rehearse conversations, playing both sides…backing up, taking different tacks, etc. Sometimes I’m just thinking out loud. I’ve done it for so long, and do it so much, that I can’t understand when people say that it’s “weird” or “creepy”. What, you don’t do it? 
I think that’s enough of my oddities for now…