1. Can’t get off the phone: Calling during emergency is one thing but calling just for the heck of it is another. I have seen many people who use airplane as a time to catch up with old friends or relatives whom they haven’t called for a while and sometimes they keep chatting up until the minute the plane takes off. Also most of the times such people are loud, who wants to listen to your conversation.
2. Seatback knockers: I have heard tons of stories about inconsiderate recliners who keep pushing the seat beyond its limit but have you been annoyed by the person behind your seat who keeps tapping/knocking the seat sometimes by leg, sometimes by hand, head and what not.
3. Recliners: I am not even going to elaborate on this one, i think there are multiple incidents about these people resulting in having them de-board the plane.
4. Large bags: I know almost all airlines charge for checkin bags now but that is not an excuse to bring your large sized suitcase as a carryon. I even read a blog post offering this as a tip to travelers to escape check-in fees.
5: Not following boarding order: Zones, groups, seat numbers these are some of the thing you need to pay attention to in your boarding pass. If you have the boarding pass no one can deny you the seat. Trying to cheat the boarding order is not going to get you a better seat in any way.
There are plenty more but this makes my top five list. Are you aware of any more annoying habits? Let me know in comments.