Optimus Prime (Transformers)
In the Transformers television and comic series, Optimus Prime is the leader of the Autobots by right of his possession of the "Matrix of Leadership." In some versions of Transformers continuity, he is only the most recent Autobot leader ("Prime" is akin to a title, not a surname).
In the original U.S. television series (known as "Generation One" or "G1"), Prime transformed into a semi-trailer. His comrades included Jazz, Ironhide, and Bumblebee. His enemy was Megatron, the leader of the Decepticons.
In Transformers: The Movie, Prime sustained terminal injuries in battle with Megatron, and leadership of the Autobots fell to Ultra Magnus, and later to Hot Rod, whom the Matrix transformed into Rodimus Prime.
Toward the end of the television series (the final season of which was set after the movie), Prime was resurrected through the offices of the Quintessons and resumed leadership of the Autobots.
In subsequent editions of the Transformers toy line, it has become tradition to name the leader of the Autobots (or good-guy equivalent) Optimus Prime or a similar name such as Optimus Primal.
The same naming tradition also extends to the Decepticon leader, Megatron. (Megatron, interestingly, often undergoes a resurrection after his inevitable death in the accompanying cartoon television series into Galvatron, with accompanying toy.)
In March 2003, a man from Ohio in the United States, legally changed his name to Optimus Prime. See Optimus Prime (person) for more information.