The thing I hate most about cycling: Other cyclists.
Cars treat cyclists like crap, and as an aggregate we deserve it. Cyclists routinely run red lights weaving through pedestrians and cars as they cross the street, run stop signs cutting off cars that have begun to cross, ride the wrong way down one way streets, take to sidewalks when the road is slow, cut in front of turning vehicles while continuing forwards, etc. etc.
I wish more cyclists behaved, so we could start expecting cars to treat us fairly.