My #1 most hated habit that other drivers do is ride or tailgate you at an intersection. I drive an old '90 Ford Ranger, standard transmission. And when I look in my rear view and can't even see the lights of the guy behind me, it makes me WANT to stall, roll back, and screw up the idiot's bumper, because, unlike him, the scratches on my truck would probably be an improvement.
These people make me nervous, which makes me rush, which increases my chances of stalling and damaging his car.
So don't ride other people! Give 3-4 feet of clearance because stalls do happen!
What annoying habits do you hate the most?