Most of my pet peeves are driving related. Two off the top of my head...
People that drive as if they own the entire road and the rest of us are trespassers in their domain. I'm sure you've seen them. They generally fall into two camps: those who drive like maniacs and whip in and out of traffic lanes without signaling, or the opposite, those who drive 10-15 mph below the speed limit in the passing lane and refuse to move over to allow traffic through.
Second driving pet peeve - and this one happens to me at least a couple of times a day lot for some reason. You're sitting a few cars back in the left turn lane and the green arrow turns green. Invariably, the guy at the very front of the line has either fallen asleep while waiting for the light, or is busy playing with his cell phone/stereo/kids/pets/whatever. In any case, the light is green for 15 seconds before he decides to step on the gas. But does he move quickly? No. He sloooowly takes the corner as if he were towing a 60-foot boat. Because he has taken so long to move, he is the only one who gets to turn before the light turns red again. Argh!
But of course, I am a perfect driver myself.