There's only two things that truly piss me off.

#1: Distracted / Lazy / Underskilled Drivers
I don't give a damn what you do for a living, but when you're behind the wheel, driving the god-damned car is the #1 priority.

Do not talk on the cell phone (hands-free or no, the distraction remains).
Do not read or eat or put on makeup.
Do not fuck around with your iPod either.

Be alert and realize the effect your driving has on other people.

And lastly, stay right except to pass.

#2: Rudeness
This complaint takes so many forms, it's tragic and also infuriating.
It seems to me like the very principle of common courtesy is lost on most people nowadays. And it seems to get worse with every passing year.
Does anyone still believe in the concept of saying "please" or "thank you"? Whatever happened to being considerate of one another?