Fallout New Vegas

The game's story takes place in 2281, 204 years after the Great War, 120 years after the events of Fallout, 40 years after the events of Fallout 2, 4 years after the events of Fallout 3, and 6 years before the events of Fallout 4. It is set in the area of the Mojave Desert, now called the Mojave Wasteland, where three major entities are vying for control of the city of New Vegas and the power generated by the Hoover Dam: the military forces of the New California Republic from the west, Vegas' mysterious ruler Mr. House and the slaver army Caesar's Legion from the east.

The player character is the Courier, who was originally hired to deliver a package to New Vegas but is intercepted by a man in a checkered suit and a group of thugs. They steal the package, the checker-suited man shoots the Courier twice in the head and then leaves them for dead in a shallow grave. But that's not the end.

The Courier is rescued by a robot named Victor, who brings them to Doc Mitchell in the town of Goodsprings, who saves their life and nurses them to health. Once the Courier completes their medical checkup, they're sent out into the open world of the Mojave to track down their would-be killer and in doing so, decide the future of the wasteland and its inhabitants.

Endings
The game's ending is dependent on what actions are taken during the course of the story, with separate ending slides for each major location, political faction, and recruited companion. The Courier is influenced to take one of four possible ending paths; all four paths culminate in the Second Battle of Hoover Dam where the NCR and Legion clash for the future of the Mojave and New Vegas.

Currently, there has not been any official confirmation by the publisher, the developers, or subsequent games in the series for which ending of Fallout: New Vegas is considered canon.

Mr. House: The Courier will assist the martial lord of New Vegas in setting up New Vegas to become the dominant power in the Mojave, safe from the exploitation of the NCR and the bloodshed of the Legion.
The Legion: The Courier will defeat the enemies of Caesar, allowing for the strength of the Legion to crush the NCR at Hoover Dam and claim all of the Mojave in the name of the Son of Mars.
The NCR: The Courier will mend the dire circumstances faced by the New California Republic's annexation of the Mojave and further the Old-World values of democracy.
Independent/Yes Man: The Courier will depose the tyrant Mr. House and push out both the inefficient NCR and the tyrannical Legion to take the reins of New Vegas for themselves with the aid of their robot partner Yes Man.