I really get annoyed by business travellers talking really loudly about their work on their cell phones. It's almost as if they want everyone around them to hear how important they are. Yes, you're important and you travel a lot and don't have any other time to make calls, but you don't need to yell at the top of your lungs (this is especially bad when it's a sensitive conversation - like one instance where the pax was talking about who they're going to lay off).