Inconsiderate people bug me. Like when I am happily cruising down our country road doing the limit (OK, I confess, sometimes a little more) and someone on a side road, pulls up to the stop, reads War and Peace and just before I get to the intersection pulls out in front of me. And pokes along, accelerating like a Model T and decides that 45 in a 55 is just fine and there's nowhere to pass.
Another inconsiderate type: In a parking lot, some lard butt without a handicapped tag has to block a lane, holding up 5 other cars so they can wait for a person to search for keys, load groceries, then search for keys again, then get their kids belted in, then fire up and back out. The lard butt (LB), then takes the space. Said LB would be better off by finding any space available, regardless of how far it is from the door and get a little exercise. And everyone else would appreciate it if the LB would at least pull to one side of the lane so others could get by.
Litterers, smokers who toss their butts, etc. as other have said.