First and foremost... I hate people failing to chage lanes when an emergency vehicle (such as a police cruiser) is on the shoulder of a highway. By far, one of the best new laws ever introduced in this province. As a matter of fact, when I get pulled over, I exit the highway first. The officer sometimes gets pissed, but when I explain that it was for his own safety (and mine), he appreciates it.
Biggest pet peeve, is left laners! I mean, if you intentionally drive in that lane excersing your right to drive at, or under the speed limit, then you are breaking the law .... that left lane is for passing! I would argue that it's a worse offence than speeding (at only 20k over) as you piss off the guy behind you, making him tailgate and become even more agressive. Yes, people are responsible for thier own actions, but any cop or driving insructor will tell you to get away from agressive drivers.