I have to give another vote for people who try to drive up my exhaust pipe because I don't want to go over the speed limit. Although it is quite funny when they go past me only to get stopped at the traffic lights 100 yards ahead.

People who I find coming straight for me on my side of the road at double the speed limit having bounced off the side of a bridge (the police car behind them at the time hadn't started to speed up or put their light on yet). I woke up with a paramedic asking me my name (I wasn't driving for that one).

Special mention has to go to the guy with a caravan who mistook a slip road for a lay-by. OKay, it was a VERY sharp left ... but really. He ended up with a convoy of re-enactors having to send some guys from the front vehicle with a polite message regarding his mistake along the lines of "move it or we'll move it for you".

people who tailgate even though you are travelling at the correct speed (in town), and, people who drive at 40mph where national limit applies and continue at same speed through towns / villages.

"Average Speeders" I call them. We have a section of road by us where it goes from 60, to 40 to 30. Every and I mean EVERY morning, some eeejit will do 40 through the 60, causing an enormous tailback, then sail away at 40 through the 30 zone...past the two schools...grrrrrr

I get annoyed on the motorway when people suddenly move out from a slower lane to a 'faster overtaking one' with no trafficator switched on, and probably not checking the mirror before hand either.

lorries and buses even do this dangerous manovere. I wish that the cops were more hot on this.

Soviet (put em in the Gulag)