What is another word for "agent"?

Roget's Thesaurus (1911) lists these synonyms for "agent": accession, advocate, agency, agentship, agree, agreement, ambassador, anaesthesia, anaesthetic, anaesthetize, and, appointment, arbitrator, architect, assignment, attache, attest, attorney, auctioneer, author, authority, bagman, bailiff, banker, bargain, barter, bear, benumb, bewilder, bird, blind, blunt, bond, brevet, broker, bull, business, buyer, cadger, callous.