Are you a car horn honker? Are you a frequent or sporadic honker? Or are you generally on the receiving end of the honk?
I had to honk at some dingus yesterday that had no idea where he was going, kept switching between the straight-and-left lane, and the right-only lane (my lane), and, when he got to the light (green, btw) he decided he didn't need to be in my lane anymore and blocked me from turning while waiting to get back in the left lane.
I also tend to give a little blast when I'm the 2nd or 3rd car at the light and the lead car hasn't gone after 2-3 seconds. What gets me, at least in my experience, if it's two lanes, BOTH cars in the lead sit there until someone honks more often than just one car not moving.