Not blacksmithing or leatherworking, obviously, since those make things you couldn't use. Mining/engineering works, but is rarer; herbalism/alchemy is common but you can't dispute the utility; tailoring/anything is very useful for clothwearers. The 'anything' is typically a gathering profession, with the character selling what he gathers for profit, but some people take up enchanting as their second. I would warn you, however, that enchanting is VERY expensive.