Handles

"" was the name given by the Eleventh Doctor to a Cyberman head that he had obtained from the Maldovarium Market, and subsequently repaired. It went on many adventures with him as he searched the mysterious Trenzalore.

Handles is also commonly referred to as Cyber head, he is one cool guy.

Outliving the residents he had chosen to protect, Handles was the Doctor's only companion during his first three hundred years in Christmas. The Doctor kept repairing Handles as best he could, but he lacked enough spare parts and it eventually broke down. Before shutting down, Handles finally fulfilled an order the Doctor had given it prior to landing on Trenzalore: reminding the Doctor to patch the TARDIS phone back to the console. Handles' death reduced the Doctor to tears. (TV: The Time of the Doctor)

Behind the scenes
Handles is strikingly similar to the character Wilson in the 2000 film Castaway. As the main character who is stranded somewhere talks to him, both have faces and not bodies, and they both "die" (as in Wilson's case, the main character loses the ball when he builds a raft and tries to head back to land), reducing the main characters to tears.

Trivia

 * Technically, Handles is one of the Doctors longest, continually, serving companion, having been with him for over 300 years. (Although it is unknown exactly how long he was travelling with Susan.)