The One

 is a undetonated bomb in Fallout: New Vegas, which only appears if the player has chosen the Wild Wasteland trait.

Characteristics
The Big One is an undetonated nuclear bomb found northeast of the Ranger Station Bravo which only appears if the player has chosen the Wild Wasteland trait. You can salvage components (energy cells, microfusion cells and 2 sensor modules) with a science skill of 60 or more. You get +1 radiation when next to the bomb. There are three super mutant masters near it (one with a missile launcher, one with a light machine gun, and one with a minigun, the weapons the mutants have may vary). There are also a couple Glowing Ones roaming around in this area. It may be possible to draw the super mutants to the southwest to the nearby Ranger Station Bravo to enlist the help of the rangers there. Also, there are 2 rangers sleeping on makeshift beds right where the super mutants are. If you talk to them they will walk back to Ranger Station Bravo.

Tip
Bring a sniper rifle and sit on the big rock north of Ranger Station Bravo. Use it to shoot the Super Mutants one at a time, that way all 3 won't charge you at once. Should be fairly easy to beat them with this method.

Trivia
It is a reference to "The Big One" firework strapped to Buzz Lightyear's back in | Toy Story