What is another word for "runner"?

Roget's Thesaurus (1911) lists these synonyms for "runner": ambassador, apparitor, applicant, aspirant, bag, bagman, bearer, beggar, bellman, bidder, boy, bum, cable, cadger, candidate, canvasser, carrier, case, child, chore, claimant, client, commissionaire, competitor, core, correspondent, courier, crier, dak, delivery, diplomatist, electronic, emissary, envoy, errand, estafette, express, flag, flower, gentleman.