I’m just gonna take this time to set up the skeleton of the Neutral Scourge faction rep grind.
TL;DR: Operation: Shieldwall with a dash of Netherwing buildup, but with zombies. You don’t get Invincible at the end.
You start off as Unfriendly with the Scourge, with a decent-length questline that will raise you to Netural. At this point, you can walk into Scourge areas without having to listen to the masses throw asshole-y comments your way. (Death knights probably start at Neutral, questline bumps them up to Friendly. Probably makes them uncomfortable, definitely makes the mortals uncomfortable.)
At Friendly, you have more story-progressing questlines, and then start your descent into Dailies Hell. Access to vendors.
Honored – story-progression questlines, more Dailies Hell. Access to blue recipes.
Revered: Story quests, dailies hell. Epic recipes, blue gear, a couple vanity recipes, trinket that allows you to call upon the warriors of the frozen north.
Exalted: End of the story questlines. Epic recipes, title, epic gear (equal to or below raid tier), tabard, and unique mount. I’m thinking undead proto-drake or a ghostly (you could say invisible) horse. Casual mention that whenever Arthas goes back to trying to destroy the world, your character is at the top of his hit list. It’s a compliment.