In Arathi Highlands, there is a quest named "Hints of a new Plague" - Hints of a New Plague? - Quest - World of Warcraft
It requires you to kill the npc, named "Forsaken Courier" - Forsaken Courier - NPC - World of Warcraft .
The Courier travels with a group of 4 bodyguards all the way from Go'Shek farm, to Tarren Mill fallowing the road. As soon as you kill them, they will spawn again in their starting location - Go'Shek farm (the house left of the main road) . They don't do so much damage and as a level 33 paladin i just AoE them using Consecration and Retribution Aura. As opener i use excorsism on the courier. After you kill the group they will respawn again and again and again. You have few seconds, depending on where you kill them, to drink and heal if you want to. At my level killing them gives me around 700xp (unrested). The Npcs can be looted and they drop some good greens and silver
You don't need the quest to see the courier, he patrols even if you don't have it. He is friendly to Horde!