In the 2009 film Avatar, the protagonist’s first name is Jake.
Jake Sully is a former Marine who replaces his deceased twin brother, Tommy, in the Avatar Program. Because the avatar was genetically matched to Tommy, Jake is able to operate the Na’vi-human hybrid body intended for his brother. He is sent to Pandora as part of a scientific and corporate mission.
Sam Worthington plays Jake, while Zoe Saldaña plays Neytiri, the Na’vi hunter who teaches him about her people and their environment. Jake’s growing loyalty to the Na’vi places him against the human forces seeking to mine unobtanium beneath their home.
The character is commonly called Jake Sully, not John Sully or Jack Sully. His surname is Sully, and the film’s title refers to the remotely controlled bodies rather than to Jake himself.