Outrunners

An Outrunner in World of Warcraft seems the be a mix between a messenger and a scout. Many things in WoW have this name.

Alliance Outrunners
The Alliance Outrunners are four (sometimes just three) level 21-25 elite NPCs in the Barrens, usually near the south road. They have a tendency to gank unsuspecting Horde players, and these victims usually return to gank them at a higher level in return.
 * Members:
 * (Night elf)
 * (Night elf)
 * (Night elf)
 * (Human)

Blood elven outrunners
Group of blood elves that take care of shuttling goods between Sunstrider Isle and the mainland (which is Silvermoon City). Their travels are not devoid of danger as the Ruins of Silvermoon, which they have to go through, is controlled by the wretched and defective arcane guardians.
 * Members:

Centaur outrunners
Different centaur clans have outrunners.
 * Members:
 * Galak tribe in Mulgore:
 * Gelkis clan in Desolace:
 * Kolkar clan in Durotar:
 * Magram clan in Desolace:
 * Kolkar clan in Durotar:
 * Magram clan in Desolace:
 * Magram clan in Desolace:

Dark Horde outrunners
The Dark Horde have outrunners in the Redridge Mountains.
 * Members:

Gnoll outrunners
Some gnoll packs have outrunners.
 * Members:
 * the Riverpaw pack in Elwynn Forest:

High elven outrunners
The Highvale Outrunners are a high elf outrunner from Quel'Danil Lodge in the Hinterlands.
 * Members:

Night elven outrunners
Night elves have outrunners to watch out for invading forces in Ashenvale.
 * Members:

Tauren outrunners

 * Morin Cloudstalker

Items related to outrunners
There are several items which outrunners may use:
 * Outrunner's Bow; which is a bow which can be bought by pvp'ers contesting in the Warsong Gulch.
 * Outrunner's collection; which is a whole collection of items with the name outrunner as prefix.