Rikumaru

is one of the deer owned by the Nara clan.

Hidan and Kakuzu arc
Rikumaru stood beside Shikamaru's side when he swore to Hidan that his clan would keep him buried here for eternity. He later followed Shikamaru to the edge of the Nara's forest.

Trivia

 * In the anime, Rikumaru stood by Shikamaru's side while he buried Hidan. However in the manga, Rikumaru is not seen until Shikamaru meets Sakura, Sai and Pakkun at the edge of the Nara forest.
 * Antlers like his are a key ingredient in a variety of medicines.