No turn signal. Use of the turn signal lets other drivers know that you are about to slow down and turn. This gives drivers some notice before your brake lights go on. Using the turn signal in the middle of a turn is completely useless and defeats the point. We already know you're turning. I notice cops do this all the time.
Slow turning. I know SUVs tend to roll over but it won't happen at 10 mph. Stop turning at 2 mph. I hate you.
Stopping in the entrance to a parking lot. This is especially dangerous for the people behind you as they don't know you're a moron and about to block them. So while you're sitting there jerking off or whatever you're doing, the person behind you is coming close to getting hit by oncoming traffic. Even though this is completely your fault, they would probably receive the ticket. I've had to turn into exits several times to avoid being hit because of morons doing this.
Tailgating. You're not getting anywhere any faster by riding inches away from the car in front of you. Especially if they're behind a slow driver. When people do this to me I slow down. Sometimes they learn and back off, but usually they'll stay right there and start flashing their lights and honking.
Overuse of brights. The only real times you need to use brights is if you're driving down a curvy road you're unfamiliar with or when you're driving somewhere an animal could run out in front of you. Other than that, turn your brights off. And don't get pissed off when you leave them on and somebody flashes their lights at you. That isn't them being a jerk, that's you being stupid.
Driving under the minimum. Roads were made for commerce. Not for you to drive your grandkids around at 20mph in a 55mph zone with a 40mph minimum. This is an offence known as obstructing the flow of traffic. If you can't drive 40mph then sell your car and start taking a taxi. The 60 people behind you shouldn't be late for work simply because you're incompetent.
Trailing other cars through a red light. It doesn't matter if you're in line to go through the light. Once it changes red you're supposed to stop. All too often in turning lanes I'll see 6-7 cars in a row behind the stop line running the light after it changes to red. Where are cops when you need them?
More to come whenever I feel like adding things.