The worst of the rule breakers are the wrong-way cyclists: The ones who think that riding on the wrong side of the road is safer because they can see cars coming. They are wrong.
Riding on the wrong side, and on sidewalks, puts you in places cars would never expect you to be, and so they're even more oblivious.
If you're going to break rules, break the right ones and understand the impact fully.
Behavior of some riders surprises me, they'll switch between pavement and road whenever they wish to. Just yesterday, someone jumped from the pavement onto the road a few metres ahead and the car in front of my was caught by surprise. Then there's people who will zoom past stop signs without considering there might be other vehicles and ignore them completely. I get what you're saying.
I always try to stay on the road, stop at stop signs, just ride as if I were a car. I've never had a close-call and always try to make my movement obvious.
Had this happen to me recently on a 55mph highway with no shoulder. The other cyclists didn't even take it upon themselves to move, they just headed right toward me.
It was one of the closest calls I've had. I'm pretty sure I would have run into him head on if I hadn't had a bright front light.