From Derek at BlogTO as a response to Sgt. Tim Burrow's Top 10 list of driver complaints. (BlogTO is good at these lists):
10 - The close pass
9 - Lack of bike lanes
8 - Cars parked in bike lanes
7 - Potholes
Yes, potholes, but also utility cuts, which in some way are even more irritating. A utility cut can create a wide, sharp drop from which you can't easily escape; or the cut can run below you for blocks creating the roller coaster, or "mutton bustin" (sheep riding), effect - also unavoidable.
6 - Winter
5 - Other cyclists
4 - Car doors
3 - Streetcar tracks
Derek suggests the bunny hop, but that's a bad idea. CAN-BIKE recommends taking the tracks as close to 90 degrees as possible - slow down and cross the tracks at a sharp angle.
2 - Oblivious pedestrians
1 - Sudden right turns (without signaling)
This is Derek's key complaint, and though it is rarer than the others, it's a biggie. I agree, complete disregard for a life. A more minor but related complaint is the right turn from the left of cyclists at red lights - you wouldn't do that with a car so why do you think it's okay with a bike?
Honourable mentions: jerks who bypass the line of cyclists at red lights, slow e-bikes that need to be passed (but that can be nice to draft!), riding north from downtown (it's all uphill), and the constant threat of bike theft.