Probably my worst habit is that I tend to chew the shit out of the collars of whatever shirt I happen to be wearing. It's something that came about from gaming and extensive computer use, I tend to only do it when sitting at a computer or in front of a TV. I've gotten it under pretty decent control of late, but I noticed it happening again now that my stress level is high.
Also a strange habit of mine, I cannot sleep at night without one of a very specific few stuffed animals under my arm. It used to be one in particular, a wrinkles dog I've had since I was 7 or 8. That dog became so worn out, that in around 2005 I had to adjust to a different animal lest I ruin it completely. So over the course of a year, I came accustomed to this trio of near-identical bears made by Fiesta. Instead of the wrinkles dog, I now sleep with any one of these three bears under my arm every night, no matter where I am. Of the 1000+ stuffed animals I own, it HAS to be one of these three, or I literally will not sleep. And if they come dislodged from under-arm while sleeping, I tend to wake up (fully or partially) and grope around until I find it again.