Not indicating doesn't bother me too much, especially if they're just changing lanes on the motorway and its relatively clear. But its annoying when they're turning in a side road and I'm trying to pull out but they don't indicate.
Tailgaters I can't stand at all, suddenly my brake pedal becomes fun to press. As said, if you're in a rush leave earlier. Don't put my back bumper at risk just because you want to speed, I'm happy to let you overtake if its clear. I'm not going to break the speed limit just for you.
Going slow in NSL is understandable if its say going 40 on a Single Carriageway NSL (60) road as they can be pretty bendy. And if they're going like 30MPH you can always overtake if its clear. On Dual carriageways, theres always the right hand lane.
Cyclists aren't too bad, they're doing a favour to the environment and not driving their cars. But some are absolute ***** like drivers can be.
Middle Lane hoggers don't bother me, I can use the overtaking lane to get pass.
People who pull out infront of you and block like half of your lane and you need to slow down to let them go really annoys me. You have to give way to traffic on the road, not vice versa. Same with roundabouts when they can clearly see me coming. Luckily I'm a relatively calm driver and I don't really rage at any one or honk unless it was a close near miss.
Using lights in the day doesn't bother me unless its full beam. But driving in the dark without lights is very dangerous although they normally realise quickly!
Any others? Undertakers. They see the left hand lane being clear for 500m and speed past you at 85MPH on the left then indicate to move back in front of you. I'd move over to the left on motorways/dual carriageways for any one who wants to drive faster if you're not tailgating me.
Going straight on roundabouts on the right hand lane. Always happens on this roundabout near me. Normally theres more traffic on the left hand lane, they speed past on the right hand lane and try and go straight.
Last of all, TAXI DRIVERS OMFG YOU DON'T OWN THE ROAD. JUST BECAUSE YOU WORK ON THE ROAD. Everything they do infuriates me but sometimes theres a few normal ones. /rant