Rep: Sporeggar

Tucked away in the West corner of Zangermarsh is a mostly peaceful race of mushroom people called the Sporeggar. These little guys have a BIG problem. It seems they have become the diet for many of the other inhabitants of the marsh. Gathering rep for them is not difficult just tedious. Both the Alliance and Horde factions will start out as Unfriendly but it won't take you long to get you to at least neutral.

Gathering stacks of 10 Glowcaps and turning them into Msshi'fn will get you to Neutral.
Gathering either 10 Mature Spore Sacs (the easier option in my opinion) or 6 Bog Lord Tendrils and turning them into Fahssn you can get up to Friendly.

If you don't want to gather items and turn them in you can do the grind method as well. Bog Lords will give you rep until end of Honored. Marsh Dredgers and Marsh Lurkers will give rep until the end of Revered.

Once you hit Friendly Fahssn will send you to Sporeggar and some repeatable quests will open up to you from Gzhun'tt. Now that we're Friends and the repeatable Now that we're Still Friends... has you killing the near by Bloodscale Slavedrivers and Bloodscale Enchantresses. Bring Me a Shrubbery! and the then repeatable Bring Me Another Shrubbery! Sanguine Hibiscus can only be found in the Coilfang Dungeons but if you are farming them for Cenarion Expedition Reputation it might be an option you want to explore as well. That or if (unlike me) you are willing to just PURCHASE your quest items (shutter) you may be able to find them on the auction house. Both of these repeatable quests are good all the way through exalted.

Now there are many reasons to go after this particular reputation if you are an achievement pursuer. Reaching exalted with Sporegger will grant access to a pet which will count towards the Lil'Game Hunter Achievement, it is one of the reputations needed for the Diplomat Title, and it will also give you access to a Tabard that counts towards the 25 Tabards achievement.

Happy Grinding!