Generally pretty annoying - the arrogance to believe that what they want to hear is so much more important that everyone else.
However at the weekend I saw one that took the biscuit.
Everyone was dancing around to Passion Pit's hit from the hit parade, Sleepyhead. It ends, and the playlist continues.
Girl enters room, declares she missed the song and wants to hear it again.
Takes the ipod out the dock so all music stops and then starts clicking away.
Everyone stands in silence looking at her, while she shows that she was incapable of actually using an ipod (when I picked it up she was looking in Extras). Then places ipod back down and walks out moaning.
Ipod is replaced, and awkward dancing is recommenced