Perhaps my biggest pet peeve is people ignoring traffic rules or more specifically people purposely violating traffic rules to be perceived as polite. An example of this that really gets my blood boiling is when someone is going straight or turning right but waves you through a left turn. Just go, then I can go. That's how it works.
Riding a bike makes this conundrum even worse. On my ride to work there are two 4-way stops, round trip = 4 4-way stops. In three cases I am going straight or turning left. I guess a lot of people don't understand the physics of how a bicycle works. It is much easier to resume the speed you were once traveling if you don't come to a complete stop. If another car arrives at the stop first, I start to slow down to give them time to continue through the intersection. But what typically happens is that they just SIT THERE and wait for me to come to a complete stop then wave me through. YOU ARE NOT HELPING ME ASSHOLE. Compounding this problem are the cyclists who ignore stop signs. HIT THEM.
That is all.