People that just won't move on the plane. Like, they'll be sitting with their legs all in the aisle and you're like, "Shit, shit, gotta pee gotta pee." and they just look at you, like you're the one being annoying.
Also, children that run screaming around the terminals.
And the really shitty buggies you put your luggage on, because they never turn when you need them to, and pushing two at one time sucks. D: