Earthwarden

Earthwarden is a two-handed feral druid mace. A level 70 druid in Dire Bear form with 3 points in the Thick Hide feral combat talent would gain 2750 armor while wielding this mace. This in addition to the defense, expertise, and attack power bonuses makes the Earthwarden ideal for druid bear tanking.

While you can get stronger weapons for doing damage in cat form, Earthwarden is the best tanking weapon for druids outside of the 25 people raid instances, and thus worth grinding reputation for.

Source
The Earthwarden may only be earned by reaching with Cenarion Expedition, where it may then be purchased from Fedryen Swiftspear in the Cenarion Refuge in Zangarmarsh for.