Hmmm most things have been mentioned before, but mine are........
Middle lane muppets, they cause motorway queues as everyone has to come out to overtake them, bunching up the traffic and often the inside lane is empty!
People who wander about on roundabouts and cut across you by not keeping to their lane, often haven't even a clue that you're there.
Inconsiderate parking is one that really annoys me, especailly around the school about a mile from where I live, it's a no go zone around school collection/dropping of times, parked all around the junction, blind bends, doors open, stood in the road, idiots!
People who've no idea how to use roundabouts in general! You pull up, slow down and stop as they have right of way, and they sit there, waiting, waiting for what!? They look at your blankly, so then they get the roar away treatment! Or those who don't indicate, leaving you playing the guessing game as to which way they are going, or you sit there waiting as they are still signalling right, but then turn off left before they reach you! It's not rocket science!
Drunk drivers. It's not clever at all, it's just far too dangerous to risk no matter how little you've had.
Similar to Vicky's one about people who seem to drive at 45 mph or so no matter where they are! On the big wide main roads, 40 mph, then get to a 30 mph zone, still 40 mph! The other ones are those who fly through the villages and towns, then slow down when they reach the national speed limit roads where they can safely get up to speed. I was overtaken going over speed bumps the other night by a transit van doing about 50 mph in a 30 zone, suddenly saw lights behind me, on my rear spoiler near enough, then coming up to a blind bend on a hill over speed bumps it over takes me! Get to the national speed limit a few hundred yards later, it had slowed down to 40 mph!
People who brake unnecessarily! The sort who are contantly hovering over the brake pedal at the slightest hint of a corner, or oncoming traffic etc., instead of easing off and simply slowing down through engine breaking to shave some speed, then gently building up to speed again, they suddenly jab the brakes, lose all momentum and end up in a flap as it won't pull in 5th now they've lost all the speed!
Tailgaters. It really annoys me, they get so close that you know if you had to brake suddenly they wouldn't stand a chance of stopping, and it's you they'll hit. When you can't even see their lights you know they're close, and often it's in situations where there is no way you can or want to go any faster, as you are either obiding by the limit or are in a queue! I have in the past felt the need to drop a gear, make the brakelights come on with my left foot without braking, and stamp on the accelerator at the same time. That wakes them up and gets them puzzled. I'd not thought of moving the gear lever across and lift the gate to make the reversing lights come on, certainly one to try in extreme cases!
Mobile phone users. Despite it being against the law, you still see so many people holding phones while driving. I'm not kidding, I was followed on the motorway by a woman on the phone AND doing her make up at the same time. She was on autopilot, I just made my brakelights come on again, a favourite of mine, without braking, and it took her a while to even notice, she was tailgating as well. When she finally realised I could be braking you could see the shock and panic in her face!
Well...............I think that's quite enough for now.........there are other things that annoy me, but these are the main things that cause the most annoyance! I'm not an angry driver........normally, it just depends on how badly someone drives around me and how dangerous they are.

Pete
G reg 360 GLT, G reg 340 GL Variomatic, plus many more..........