Zero Point Energy Field Manipulator

"The Zero Point Energy Field Manipulator is not a toy, Alyx"

- Doctor Judith Mossman

The Zero Point Energy Field Manipulator (more commonly known as the Gravity Gun ,or by Gordan Frohman, The Claw) is a tractor beam-type weapon that was originally designed for heavy lifting and the handling of hazardous materials. At its core is a substance that appears to be Xen crystal. Introduced to the player by Alyx Vance shortly after arrival at Black Mesa East, the Gravity Gun soon becomes an invaluable tool in Gordon's arsenal and is considered one of his trademark weapons.

Usage
The gun has two basic modes, the first (primary fire button) punts objects. This is useful for clearing out barriers and moving heavy objects. The secondary mode (secondary fire button) picks objects up and holds them in its field. These objects can then either be dropped (by pressing the secondary fire button a second time) or launched (by pressing primary fire). In combat, the Gravity Gun can be very useful depending on the types of physics objects available for use as ammunition. The gun can also be used to pull objects over from a distance, allowing you to access supplies or other objects that would, otherwise, be out of reach. It's also worth noting that while the gun can manipulate many objects, some objects are too heavy or bulky to be picked up. However, some of these objects will still move when punted.

Besides its obvious use as a weapon through its ability to hurl heavy objects at enemies, it is also utilized in many other ways. Clearing heavy obstructions, holding up objects as portable shields against gunfire, returning live grenades to their owners, knocking over turrets, removing and reprogramming hopper mines, removing rollermines from vehicles, dragging objects over from a distance, etc.

The Gravity Gun appears to be quite heavy, as Alyx Vance and other characters that attempt to use the gun have some trouble lifting it.

Finally, while the standard Gravity Gun can't pick up organic material, it can be used to effect against some enemies. Manhacks, City Scanners and Shield Scanners can all be held in the gun's field and launched. The gun can also punt Headcrabs and Antlions, inflicting minor damage. Doing so also knocks the latter over, exposing their weaker undersides.

The inner workings of the gun is unknown. However, the gun's name suggest it is powered by some generator based on Zero Point Energy, but there is NO official background info....

Dark Energy Gravity Gun
Also known as the "Super" or "Organic" Gravity Gun.

In Citadel security systems, the Gravity Gun seems to simply absorb the weapon confiscator's energy, while other weapons are destroyed. In doing so it shorts out the weapon confiscator in the process, prompting Overwatch to announce "Warning, counter resonance singularity device detected. Confiscation field failure." Once supercharged, the Gravity Gun emits blue light rather than orange, it quakes in Gordon's hands and creates small bolts of energy across it's muzzle, and is vastly strengthened. It can hold larger objects, launch them at greater speed, pull with more force and even pick up and launch living creatures (specifically Overwatch Soldiers) to their deaths. Also, holding someone in the Gravity Gun's field appears to electrocute them and destroy their weapons, as the body will spark and twitch, once dropped.

The first time the Gravity Gun is supercharged is Half-Life 2's 13th Chapter, Our Benefactors, when Gordon's pod deposits him into a confiscation field and remains so until the end of the game. During this time, Gordon's HEV Suit also becomes 'supercharged' to the point of harboring 200% energy, and power chargers now garnering the ability to charge Gordon's health as well. At the start of Episode One, it is no longer supercharged, but becomes charged again after Gordon and Alyx re-enter the Citadel to stabilize the core, and Gordon accidentally enters another confiscation field. It remains supercharged until Gordon reactivates the core's containment field, at which point the Gravity Gun reverts to its normal state.

After leaving the Citadel, the Gravity Gun never becomes supercharged again. Valve has confirmed that, sadly, the Gravity Gun will never become supercharged again due to the difficulty of incorporating it into the gameplay of the level.

In Episode One and Two. it can be activated in normal use by entering the console command "physcannon_mega_enabled 1".

The Gravity Gun is present in Garry's Mod as a starting tool. However, it cannot be supercharged by any means. If the player enters a confiscation field, all weapons will be destroyed as normal, except the Gravity Gun which just sits on the ground. To get around this, the player can use several console commands which control the behavior of the weapon such as physcannon_pullforce. These commands are native to the Source Engine; they can increase (or decrease) the power of the weapon to meet the supercharged version, however it still won't affect people. This might be intentional, as the supercharged Gravity Gun's skin is used by the Physgun or Physics Gun, a beta weapon resurrected in Garry's Mod as an integral tool.

Trivia

 * The "Kicker" from the game Project: Snowblind functions exactly the same as the Gravity Gun, with the main difference being that it can be charged up.
 * The "Telekinesis Plasmid" from Bioshock functions exactly the same as the Gravity Gun, the only difference is that its used by using the player's mind not the gun and that you use your hand instead of a gun
 * The Gravity Gun bears a marked resemblance to the Aperture Science Handheld Portal Device (Portal gun) from Portal. The Portal gun also uses the same sound clip as the Gravity Gun.