traveler, traveller - a person who changes location

conveyer, conveyor - a person who conveys (carries or transmits); "the conveyer of good tidings"

dispatch rider - a messenger who carries military dispatches (usually on a motorcycle)

herald, trumpeter - (formal) a person who announces important news; "the chieftain had a herald who announced his arrival with a trumpet"

bearer - a messenger who bears or presents; "a bearer of good tidings"

errand boy, messenger boy - a boy who earns money by running errands

process-server - someone who personally delivers a process (a writ compelling attendance in court) or court papers to the defendant

runner - a person who is employed to deliver messages or documents; "he sent a runner over with the contract"