|"An experimental weapon that is currently being produced as a series of one-off prototypes, the plasma gun superheats slugs of magnetically-doped plastic and accelerates the resulting gas-liquid mix using an array of linear magnets. The resulting plasma stream is deadly when used against slow moving targets."|
|— Deus Ex description|
The Majestic 12 Plasma rifle is a weapon in Deus Ex.
The plasma rifle is launched in 2052 with one being wielded by UNATCO nano-aug agent Paul Denton during a mission against NSF forces on Liberty Island. This weapon is being phased into use first by MJ12 special operations teams, then by selected elements of military and security organization throughout the world. The first prototype of the weapon is sent to the Liberty Island MJ12 laboratory.
The plasma rifle fires three balls of plasma when the fire key is pressed. Each of these balls are very close to each other and will usually strike the target, but not on the same body part. Standing for a second before firing will reduce the spread to zero. A ball will inflict fire damage on enemies.
When the plasma balls hit something, they will explode. Each ball will release a small explosion radius that does fire damage to anything in it, no matter if the victim suffered a direct impact from the plasma ball or not.
- Reaching Advanced Heavy skill level is a very good idea for anyone that wants to seriously use the plasma rifle because they'll be able to run at full speed at that level and it will reduce recoil to the point where it barely moves the player's view when it fires. Maneuverability is vital for anyone that wants to survive a firefight, while being able to constantly fire the gun without having the gun jerk around after each shot makes it much easier to deal with groups of enemies.
- Obtain Master Heavy skill level in order to get the most out of the plasma rifle. Getting it will make most shots a OHKO against common MJ12 Troopers and will reduce the gun's spread to almost nothing.
- The explosion that occurs after a plasma ball hits something can hurt the player, so getting close to enemies before firing is not a good idea.
- The Targeting aug is always a good choice for plasma rifle users, no matter their skill level. The damage boost it provides, even at level 1, will help make the plasma rifle more effective.
- Clip mods are always a good choice for the plasma rifle, as its magazine can quickly run out because it'll usually take multiple shots to down an enemy unless the player is at Master Heavy skill level.
- Ammo for the plasma rifle is fairly rare. To get a little more ammo than what would be found normally, knock out plasma rifle-wielding Men in Black instead of killing them. Knocking them out will allow the player to grab their ammo, which is always helpful.
- Liberty Island, Paul Denton carries one at the very beginning of the game.
- Liberty Island MJ12 lab, in a security container in the armory.
- Maggie Chow's apartment, on one trooper of the Majestic 12.
- Tracer Tong's laboratory, on pedestal in the shooting room.
- Paris street, in a combat supply crate in the flat of an arms dealer, If you have Shifter, however, it will be a Railgun.
- Sub base, 2nd floor after taking minisub. It's in a water tank with 2 karkians inside.
- The plasma rifle is far less powerful than it should be in single player mode because the coding for it always uses the multiplayer damage values for the gun, regardless of the game mode the player is in. This bug was introduced in a patch. 
- Although it takes up the same amount of space as the GEP gun and the Flamethrower, it seems to be smaller when compared to the two.
- The likeness of this weapon seems to be based off the BFG9000 from Doom.