My #1 is cutting left turns. I can't tell you how many times someone has cut across my lane while making a left turn.
Dang it! Make a good, sharp left turn. Do not cut across lanes. Sorry if you actually have to turn your steering wheel more than 10 degrees.
In their defense, it's almost impossible to turn the wheel any further than that when you have your shaver in one hand, your cellphone in the other, and you're steering with your knee.
A little old lady - well into her seventies - did that to me just yesterday, cutting me off very closely. I honked at her, and when I changed lanes and passed her, she stuck out her tongue at me!