Aside from everything else.........someone who is easy to fly with whether it be an FO or a Captain. When you are at an airline, everyone can theoretically do the job and most people do. The FO's that stand out in my mind as negatives are the ones who are just not "cool". Take that how you will but what I mean by that are FO's that back you up, have a social life, are not Airplane nerds (guys or gals who's life revolves around flying) and are easy to talk to when flying. I despise FO's or Captains that are anal (There is a time and place for that but when it is clear and a million, we are configured, stabilized and cleared to land.....RELAX) I could write a book on this but to me it really doesn't have to do with flying skills but rather with social skills.