Rikumaru

is one of the Nara clan's deer.

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

Trivia

 * In the anime, Rikumaru stood by Shikamaru's side while he buried Hidan. 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.