Fat Man (Fallout 4)

The M42 Fat Man is a weapon in Fallout 4.

Characteristics
First entering service in September 2077 with the U.S. Army, the Fat Man is a shoulder mounted mini nuke launcher. The variant appearing in Fallout 4 has a slightly different appearance than in previous games. There is no longer a handle on the right side of the launcher, and instead two straight handles on the bottom. It also appears to be larger, with a rusted silver paint job.

Developers struggled to find a way to fire the heavy ammunition from a man-portable system far enough to keep the operator outside the blast radius, losing a lot of people in the process. Eventually, it was discovered that by placing a small sub-charge into the ammunition itself, similar to bullets being fired from a gun (or perhaps more accurately described as being along the lines of a recoilless launcher), the warheads could be launched a considerable distance without adding too much weight to the already heavy weapon.

When fitted with the MIRV launcher, it fires six mini nukes in a cluster that separate in midair, drastically reducing its range, but increasing its overall damage and area of effect.

Variants

 * Big Boy, a unique version with the Two Shot legendary modification.
 * The Striker, a unique version that fires modified bowling balls instead of mini nukes.
 * Nuka-nuke launcher, a unique version that deals 50% more damage than the standard model by firing quantum-enhanced Nuka-nukes.

Locations

 * Robotics Disposal Ground - Found laid on top of a car hood near the back of the scrapyard.
 * Chance of being equipped by raiders with power armor.
 * Fort Hagen - In the armory.
 * Revere satellite array - Can be found at the top of one of the towers, next to a power armor frame and a case with miscellaneous ammo and other items.
 * Malden center - Found behind a train car hugging against a wall.
 * BADTFL regional office - In the evidence locker.
 * Goodneighbor - Found behind the desk, beside KL-E-0 in the Kill or Be Killed store.
 * ArcJet Systems - Found in the room marked '2' in the Engine core.
 * Federal ration stockpile - In the main stockpile area, just inside the room with two turrets against the wall near the terminal that operates the doors (second one). This Fat Man also respawns.
 * Lexington - On the walkway where the Raider with the power armor is found.
 * Quincy ruins - being held by Sergeant Baker, who is located on top of the church in the ruins.
 * Boston mayoral shelter - Beneath the basketball court is an entrance to a cave. The Fat Man lies next to a dead soldier at the end of the cave. There is a nearby deathclaw that will attack on sight, so early on, this should be avoided until you are at a higher level.
 * D.B. Technical High School - At the far end of the old swimming pool in the northwest corner of the lowest level of the school. This is by the raider boss' bed and terminal.
 * Cabot House - In the basement near Edward's bed.
 * Boston Airport - Slightly north of Boston Airport, there are wrecked cars. Inside one is a Fat Man. From the Boston Airport fast travel location proceed East. The nose section of an airplane will be in front of you. The Fat Man is located in a van on the water's edge behind the nose section.
 * Salem - On a shelf in a bombed out store across from the chapel.
 * The Castle - Found in the armory on a shelf, next to it will be a mini nuke.
 * Spectacle Island - On the lower level of the beached tugboat containing the generator.
 * The Prydwen - Inside Proctor Teagan's store.
 * Gunners plaza - In a locked utility closet in the south-west corner of the second floor.
 * Libertalia - Carried by a random raider at the top of the main building.
 * Hub City Auto Wreckers - Carried by a named Gunner, Bridget.
 * Zephyr Ridge Camp - Carried by a trapper on the tower's top level.

Behind the scenes

 * The Fat Man may have been inspired by the real life M-28/29 "Davy Crockett", which was deployed with American soldiers in the Cold War. The main differences are that the Davy Crockett was fired via tripod, while the Fat Man is shoulder-fired, much smaller/lighter and its mini nukes have a significantly smaller yield than the Crockett's.
 * The Fat Man could only exist in its form if it used the Californium Isotope Californium-252, due to its low Critical Mass, which is the mass necessary to start a nuclear fission reaction. Though it would have been incredibly expensive to mass produce them since a microgram (one millionth of a gram) of Californium 252 costs 10$ and you would need around 2.73 kilograms (5.95 pounds) per mini nuke.