I am sure this has been brought up before on this thread but people who use their indicators incorrectly drive me completely up the wall.
The two main culprits are
1. Using indicators not to give notice that they are going to turn shortly but as they are actually turning. It's almost like they just stick their little finger out and catch it on the indicator as they turn the wheel. I assume that this is a failure in driver education, they seem to have a vague idea that there is a connection between indicating and turning but have no idea what that connection is supposed to be.
2. Is a similar lack of understanding that indicators are meant for the benefit of other drivers. Where there are two or more lanes of traffic and no dedicated turning lane I will look at the indicators of the cars in front of me to assess the likely delay. If there is a car waiting to turn across on-coming traffic I will take the other lane. It really creases my brow when the car in front of me waits until the light changes to indicate and I am stuck waiting behind them, usually for almost a full cycle of the light, while the other lane cruises past.
Also, while I am on my driving rant, people who assume that everybody drives an automatic car. I drive a manual (stick in the US) and it makes me very tense when I have to stop on a steep hill and the driver behind me comes thisclose to the back of my car. I am so worried about having a tiny bit of roll back that I end up over accelerating and roaring off like a complete hoon. Just a little bit of space would make things so much less stressful. (I am a good driver but on very steep hills a bit of roll back, maybe six inches, can be difficult to avoid)