A "nuke launcher" that can be held over the shoulder, the "Fat Man" is the most powerful, usable weapon in Fallout 3. The explosive projectile is a drastically underpowered version of the atomic bomb that can explode approximately 30 meters in front of the character and have no negative effects. Ammo is limited, and to no surprise considering the weapon uses " mini nukes" as the ammunition. There is a variation of this weapon called the " Experimental MIRV" that shoots 8 mini nukes at one time. This alternate version is effectively the most powerful weapon in the game, as well as the most awesome and unnecessary.
The name "Fat Man" is a reference to the second, and last, atomic bomb used against humans. On August 9th, 1945, "Fat Man" dropped from the bomber BocksCar and landed on Nagasaki, Japan. This bomb was made of plutonium and carried even more harmful aftereffects than the bomb on Hiroshima. It effectively ended World War II in the sense that Japan surrendered on the 15 of that month.