The Ratboy Handgun is one of the many weapons that can be acquired in the Nightmare. It can be purchased from the Frog in the Waiting Room at a price of 25,000,000 gold. It can also be obtained as a possible reward from the Ratboy's Nightmare Dungeon.
In appearance, the Ratboy Handgun resembles a modern semi-automatic handgun with all the mechanical parts required to function, though there is no need to change the magazine after shooting.
The Ratboy Handgun, like all other firearms, uses Bullets as its primary ammunition and spends 2 stamina per shot. It is capable of firing roughly faster than one round per second. Thanks to the high damage it boasts, the handgun is the most efficient way to use bullets when dealing with single targets. Similar to rifles, the player can utilize the scope mechanic, right-clicking to gain extra zoom on far-away targets.
The special ability of the Ratboy Handgun is titled 'Divine Shot', which, upon activation, spends no stamina and several seconds to charge a bullet with divine energy, shooting a single target for increased damage. In addition, enemies that have been reduced to 10% of their health or less are instantly killed when hit with a Divine Shot. The special ability's cooldown lasts for 14 seconds before it can be used again.
- The Ratboy Handgun's appearance may be based on an M1911 pistol.
- The Ratboy Handgun can be seen wielded by the Ratboy in the Ratboy's Nightmare Dungeon.
- As of the Nightmare Boss Update, it is currently the second-most expensive ranged weapon in-game, behind the Gnome Rocket Launcher.
- It is the only (ammunition-using) ranged weapon with a Special Ability that isn't an alternate attack mode.
- Divine Shot is very effective at finishing mobs with extreme amounts of health, such as the Kingrat, Mr.58, the Democan, and The Lost.
- It is possible to shoot incredibly fast with the Ratboy Handgun by performing the special cancel, causing the DPS of the weapon to increase by an insane amount and allowing enemies to be defeated much faster than normal.