People who have the audacity to sag their pants to the point where I can see their ass.
People who decide to stand in the middle of the hallway or stand to the side in one of the busiest intersections in my school.
I got late to my class 4 times in one week between 6 to 8 block, because these "gangsters" chat up a storm with the security officer there, taking up about 50% of the intersection. I think they got the message after a couple of the good-guy football team guys decided to form up and just plow through them.