For adventurers, why not ... "Master"
Interesting option. I've seen this used a lot in various fantasy literature to refer to commoners who are skilled tradesmen, or commoners who were in positions of some type of authority.
http://en.wikipedia.org/wiki/Master_(form_of_address)
"Master was used in England for men of some rank, especially "free masters" of a trade guild and by any manual worker or servant employee to his employer (his master), but also generally by those lower in status to gentlemen, priests, or scholars. "
Maybe not quite right, but it could work.
