Suburban minivan drivers! They break into two categories:
Floaters - they drift along just under the speed limit, often ignoring the flow of traffic and any/all road signs. They'll blithely do left-hand turns from the right-hand lane [or vice-versa]. They may or may not have kids, although the ones who do are usually...
Ragers - they can't stand to be behind anyone. Their minivans are driven like go-carts, either full throttle or full brake. They will right- or left-hook anything from semi-trailers to kindergarten classes and speed through school zones like they're not even there. Don't even think about drafting off them, as they will take you out.