People that go slower when they reach an incline. For some reason, the concept of physics eludes them, and they're completely incapable of realizing that they need to push the accelerator down further to continue going the same speed. There's a hill on my way home that I always end up dropping from 55-60 to 40-45 because at least one nimrod does it.
People that can't go the speed limit on a highway. I usually go about 5 over on a highway, but I'm fine if you're just going the speed limit. Hell, I won't raise a fuss about 5 below, but there's a highway around me with a 65 MPH speed limit, and people tend to drive 50-55 MPH on it.
People that brake going down a hill. Sometimes, I'll refer to coasting down hills and gaining some extra momentum as "free gas." It's a bit of a misnomer, but it's referring to the bonus momentum gained. I know people in the south are all, "boo, science!", but it's cool stuff!
People at the front of an intersection with a red light that don't pay attention. I usually watch the light like a hawk if I'm the first one, because it's not cool to hold up everyone behind me. If I'm not the first person, I can usually be a little lazy as long as I keep the car in front of me in my field of vision.
People that leave huge gaps when stopped at intersections. Bonus points if they then proceed to slowly close the gap.
People that don't realize that it's their turn to go at a stop sign and sit there. Stop signs have to be up there with traffic circles as something easy that gets messed up by idiot drivers. There have been numerous instances where I definitely stopped at an intersection after someone, but they just sat there. I end up waving them on because they obviously had the right of way, but it's annoying that I even have to tell them. It's Driving 101, folks!
People that don't understand the concept of yielding. You shouldn't be impeding existing traffic on the lane that you are attempting to merge into (or any lane that you pass over to get to that lane). Yet, I have people that do things like pull out from parking lots and proceed to accelerate as slow as possible... while I'm going 55 MPH in that lane. Bonus points if you could have pulled out into a different lane and avoided impeding anyone.
I never use cruise control if I'm driving on the highway within the city. There are too many cars on the highway to allow you to actually keep an uninterrupted steady speed. Add in other things like exiting, lane changes, merges, junctions, and you won't be on cruise control for much. But if I'm in the left lane, I'm going to make sure I'm going faster than those in the other lanes.
Now if you are talking about a stretch of hwy between cities, cruise control is much more effective.
I use Cruise Control about as much as possible, and that includes on normal roads. Of course, I'll have to stop being lazy, and manually control the accelerator if I'm in a modest amount of traffic, but if I have a decently clear road ahead of me, why not?
Most of the stuff mentioned pisses me off too.
Then there's the assholes with HID lights. They should be illegal. Our eyes are sensitive to the color blue, especially over 900000000 lumens of it. There is zero reason for headlights to be that bright. The point of headlights is to see ahead of you and for other cars to see you, not to try controlling air traffic.
Woah, buddy! Don't classify those of us with
factory HID installations into that category. My lights look white to fellow motorists not blue. I've seen the blue lights, which to my knowledge, are aftermarket products, and they are rather horrid. However, that does not represent all vehicles with HIDs.
Here's an example of what you hate (from Wikipedia's article on
High-Itensity Discharge lamps):
http://en.wikipedia.org/wiki/File:ScionHID.jpg