Here in Japan things are different from other places. The worst annoying vehicles are:
Other cyclists. In Japan cyclists ride on streets and sidewalks, can ride either way on a one-way street. Cyclists here are generally commuters, housewives, old people, and students. They tend to ride unpredictably, and cause at least as many accidents as cars.
Motorcycles. Motorcycles are common in Japan, especially the cities, as they use little gas, are easy to park, and cost little to register compared to cars. And as car drivers are generally more careful in Japan, riding motorcycles here is generally less dangerous. But motorcyclists are less careful, and often modify the exhaust on their bikes in a way that makes them louder than Harleys in America. And motorcyclists here have this odd habit of riding with their feet hanging instead of sitting on the foot pegs. Lane splitting is legal in Japan, as is passing on the shoulder, and these guys often pass too close to cyclists.
Nazi vehicles. In Japan there are nationalist nuts who long for the days of Imperial Japan with battleships in Tokyo Bay, clouds of Zero fighters in the air, and soldiers marching on parade in the palace grounds. Most of these nationalists are related to the Yakuza, or gangsters, and most of them are descendants of the Buraku, or Eta, an outcast class who were executioners, butchers, or tanners. Having been spurned by society, they somehow end up as Nazi wannabes, wearing jackboots, and coveralls which looks like uniforms adorned with old Japanese battle flags and Nazi swastikas. In Japan they drive black vans and buses which are decorated with the Imperial chrysanthemum, and old battle flags. These also have huge loudspeakers on top over which they play old propaganda songs from the 1930's, and which they also use to harangue the police, and annoy anyone within 1 kilometer.
Trash Trucks. Tokyo is a huge city which generates lots of trash, and it takes a lot of work to get it picked up and disposed of by the middle of the day. Trash truck drivers here are like moonshiners of the old south, though the police never seem to do anything to slow them down.
Kei trucks. These are the little trucks which old farmers use to get around. They have a 600cc engine, and accelerate slower than a Schwinn Stingray ridden by a first grader. Perhaps half the accidents in Japan are caused by the drivers of these little trucks, the median age of these guys is over 80.