Huan

Huan is a dog from the Silmarillion, who can only be killed by the biggest wolf to ever live. He also gets to talk three times in his life. So he understands what people say, and he has amazing senses (i.e. smell, sight, etc.). He is Beren and Luthien's companion. He goes with them on their adventures, and his life ends after fighting a wolf fed by Morgoth himself, not just fed with food, but he is fed with malace and the like. The two have a tremendous battle, but Huan ends up dying, because it was the biggest wolf who ever lived. He uses his last time talking while he is dying. His story may not be a happy story, but it is a story of love and loyalty.