The tradition of grinding rep and attainting certain rewards with neutral factions was a popular pastime in Classic World of Warcraft (WoW), and it's been expanded in every new version of retail WoW. Classes like Rogues and Druids learn about neutral factions in Azeroth and how they work earlier than others. As in other RPG games, Rogues have access to criminal or spy organizations that operate outside of the main factions, and Druids have a special relationship with one of the factions on this list.
You learn something about making nice with certain factions before level 60, but until then it's not as important. When you get to that level cap, your ability to enter raids and experience other high-level content is often limited depending on your standing with these following factions, so pay attention.
10 The Argent Dawn
It's ironic that the Forsaken are often the first players to come into contact with the Argent Dawn. The faction has a camp near the Bulwark, which is only a few steps away from their starting zone and capital city. Unlike their fanatical counterparts in the Scarlet Crusade, however, the Argent Dawn accepts any that would fight against the Scourge.
Carry the trinket they give you when riding through the Western and Eastern Plaguelands or through any dungeon in those zones to collect special Scourgestones, then turn them in to gain rep. You need to be Honored with the Argent Dawn to enter Naxxramas, and even if you don't care for raiding, it's worth it to have access to the special food and recipes that the Argent Dawn sells.
9 The Cenarion Circle
Druids know all about the Cenarion Circle and their city in Moonglade, known as Nighthaven. Druids of both factions live in peace within this faction, with the love of the Earth Mother or Elune transcending the petty arguments of war and politics. Anyone can visit this neutral city and enjoy the unique food, drinks and other items that you can only buy in Moonglade.
Grinding rep with this faction includes quests, turning in items, and fighting in certain raids. Most of the rewards that you can access as you grind more rep are patterns for armor and weapons or the actual gear itself. The Cenarion Circle is also closely connected to opening the gates of Ahn'Qiraj.
8 Timbermaw Hold
Out of all the rep grinds on this list, this one is confusing. Grinding reputation with the Timbermaw Hold will not grant access to a raid or award you with amazing gear or weapons, so why even bother?
You'll first discover that the passage through their hold is the only way into Winterspring for those that do not yet have the flight path, and then you'll find out that their vendors are selling certain valuable recipes that can take your profession to the next level. We're talking about stuff that you need for raids, such as flasks and elixirs for Alchemists, or incredibly useful items like the Furbolg Medicine Pouch.
7 The Hydraxian Waterlords
Most players don't even know this faction exists until their guild leader asks them where they are in their Molten Core attunement. Then you find yourself doing a lot of reading, and it's actually interesting. There are very long, detailed guides for players that are grinding rep with the only faction of Elementals that are friendly to the mortal denizens of Azeroth.
There are a variety of quests that lead players to the Eastern and Western Plaguelands and the Molten Core itself, so you better get attuned, which is a whole separate quest in Blackrock Depths.
6 The Thorium Brotherhood
The Thorium Brotherhood is another faction that most players never meet until they get close to the level cap. Even though they're Dwarves, they're friends with anyone willing to help them keep an eye on their former faction, the Dark Iron Dwarves and their shenanigans in Blackrock Depths.
Some players never grind very much rep with them, as their rewards are heavily focused on Blacksmithing patterns, although Tailors, Enchanters, and Leatherworkers can also take advantage of the rare recipes sold by the Dark Irons starting with Friendly status and beyond.
5 Ravenholdt
It's amazing how the main base of operations for this faction, Ravenholdt Manor, sits so close to such a busy area in Hillsbard Foothills and still remains a secret. Maybe because it's technically in the Alterac Mountains, but the easiest point of access is from Hillsbrad.
There aren't any Ravenholdt vendors and no items to gain from making friends here, only a few quests to finish and improved pickpocketing abilities and rewards. You pretty much need to be a Rogue to care about grinding rep with this faction, unlike other class-focused factions like the Cenarion Circle, who have something to offer everyone.
4 Bloodsail Buccaneers
Making friends with the Bloodsail Buccaneers is a bit awkward, as it makes you an enemy of the Steamweadle Cartel, the faction that controls Booty Bay. That means you're actually killing guards, vendors, and other citizens of the bustling seaside port. Eventually, you won't even be able to go into the city without the guards attacking you.
Why would any player do this? Because of the "Dressing the Part" quest, which rewards you with some cool pirate garb including a hat that summons and special pet, a Blood Parrot.
3 Darkmoon Faire
There's a rumor that the Darkmoon Faire is connected to some sordid cult connected to an Old God. It must be that eye. We don't care, however, because this faction has some of the coolest stuff. Anyone can collect or craft items from all over Azeroth and trade them for powerful gear and weapons.
The Darkmoon Card sets are famous for their rewards along with how hard they are to find. All of the blue cards that make up the purple sets are random world drops with the exception of the aces, which you can find on bosses in high-level dungeons.
2 The Zandalar Tribe
Seek this elusive tribe on a small island in the northwestern corner of Stranglethorn Vale, the ancient Zandalarians, from which all other Troll tribes are descended. These days they battle the rise of the Blood God, Hakkar, and they need your help. You'll need theirs, too, and if you're running the Zul'Gurub raid that's one way to get it.
Grind rep with the Zanadalari by running through Zul'Gurub. They have an impressive stock of recipes and gear for various factions and professions, so it's worth grinding right up into Exalted no matter who you are.
1 Brood of Nozdormu
Welcome to one of the oldest and most ancient factions in Azerothian history, with a direct line to the Titans themselves, no less. Getting to Exalted with the Brood of Nozdormu is a tough grind, too, since you start out at a Hated reputation (similar to the notorious Furbolg grind) and have to work your way through high-level raids like the Ruins of Ahn'Qiraj to gain rep. There's some extra rep you can get during the event that culminates in opening the Gates of Ahn'Qiraj.
Unlike other factions, this one doesn't have a Quartermaster. Your rewards come only through a series of quests, and the most sought after are the Tier 2.5 Raid sets. Many of the activities connected to the Brood of Nozdormu overlap into other popular factions, including the Bronze Dragonflight and the Cenarion Circle.