People who are considered something of an authority by others (but especially, those who are self-proclaimed) in any given specialty or on any particular topic who start to think that makes them an authority on EVERYTHING.

People who go out of their way to try to piss other people off or just make things more difficult than they would be otherwise, whether it be out of jealousy, spite, etc.

People who think the world is their trash receptacle.

Tailgaters.