The Wildhammer clan is its own faction in World of Warcraft: Classic, where all Alliance players can potentially get from Neutral to Exalted with them if they have the determination for it. The faction is strictly found in The Hinterlands, and you get 5 reputation with them each time you kill a troll mobs in the zone, or while handing in Troll Necklaces. It takes a huge amount of effort to get to Exalted with them, so the big question is, is there any rewards for getting reputation with the Wildhammer Clan?
Unfortunately the answer is no. You do not get anything from getting a higher reputation with them, except for the default 10 % lower vendor prices when hitting Honored. They don't really have anything special to sell, so this only applies to general goods sold by their few vendors anyway, which is in no way beneficial or unique.
So if you want to grind to Exalted with the Wildhammer Clan in World of Warcraft: Classic, you do not get anything except for the bragging rights of completing such a tedious challenge.