Take traffic lights, for instance. I detest it when a cyclist runs over a red traffic light. It especially annoys me when I'm doing the right thing and waiting at it at the stop line. They've come up from behind me, seen me waiting at the red light and clear thought the though look at that idiot, waiting at a red light like a lemon!.
Cyclists who run red traffic lights make all the other cyclists look bad. Since we're the minority, there's a requirement that we not stand out and make other road users think we're all damned idiots.
Be warned: if you ride over a red light near me I will shout at you, to not do so! :-)
Though to keep things balanced I should add that my current pet peeve is car drivers who are driving along side a brightly coloured cycle lane full of bikes and then they slow down to let out some car trying to join the traffic (or worse, cross the lane to go the other way) from the left.
Why can't these drivers look in their mirrors and see if the car they're letting out would be driving straight into the path of a cyclist coming along the cycle lane behind them? What makes my blood boil about this particular infraction is that the driver doing the letting out has just driven past a whole heap of bikes and should bloody-well know that the cycle lane is full of bikes and that the car they're letting out is going to suddenly present a huge stationary metal wall to a fast moving bike.