Earthwarden

Earthwarden is a two-handed mace, 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.