I would say most things across the RAF, however I would say pilot would be the most desired just because the reputation that follows it. But at the end of the day it depends on what you are interested in. Certain engineering roles can be good too and even air traffic control. However I would recommend an Officer role since it is more desirable to employers even in different fields like Finance so at the end of the day you will get a higher paying job. You will be surprised how many Military officers get employed in well paying roles in the private sector.