The only behavior I have encountered on an elevator that really bugs me is people who get off the elevator, take only a couple of steps and then stop to get their bearings or have a conversation with someone thus putting up a roadblock for anyone else entering or exiting.
Related note to that two things I cannot stand are people who stop at choke points to have a conversation with someone, check their phone, or get their bearings. At work often enough I will see people stop right in front of doors to have conversations thus blocking entry or exit from the room. Of course we all know the people in airports or malls who stop right at the top of the escalator to get their bearings instead of stepping aside first. Also I can't stand hallway blockers. Those groups of people who will walk side by side blocking the sidewalk or hallway. Its annoying enough the overly affectionate couple holding hands side by side on a narrow sidewalk, but it gets into the rediculous territory when a large family will block a large hallway walking side by side.