I've only had my rear wheel "bumped" by a car.

But I've come close to love-tapping a cyclist. We were going down hill in the same direction, and the surroundings made passing a bad idea. I was riding behind her, but to the left a bit so as not to tailgate. She stopped completely ( having been going about 20 mph ) at an intersection. I didn't have enough room on the left to go around, because of a car, and wasn't sure the bike lane was wide enough to avoid a collision. I locked my rear wheel for a split second while I was coming to a stop... When I looked back over my shoulder after I started moving again, she was unfolding a map, standing in the bike lane.