The ones that I just can't understand are those that insist on driving in rush hour traffic. Where there is no shoulder. Why do you even want to do that??
I love bicycling, but I only do it on bike trails, not public roads. Bicyclists are crazy. I recall some woman thrusting her hand out to the left vertically to signal a left turn, and turning suddenly right in front of me. I was driving to the drug store to get penicillin for my daughter, and my wife was distraught with a seriously sick child. Even on my best day, that cyclist was making a dangerous and illegal maneuver. They drive on the wrong side of the street and routinely run stop signs. They run into the rear of cars at round-abouts (rotaries). They weave into traffic. They ride three abreast. I hate the bad ones.