ace, adept, artist, authority, cognoscente, connoisseur, crackerjack(also crackajack), dab(chiefly British), dab hand(chiefly British), expert, fiend, geek, guru, hand, hotshot, master, maven(also mavin), meister, past master, proficient, scholar, shark, sharp, virtuoso, whiz, wizard

pro, professionalconsultant, hired gun, specialistaddict, aficionado(also afficionado), buff, devotee, enthusiast, fancraftsman, journeymanall-rounder(British), jack-of-all-trades, Renaissance manmistress