Created by Dr. Eli Vance
and the scientists of the human resistance movement, the Zero-Point Energy Field Manipulator (better known as the Gravity Gun) was actually intended to be used to move hazardous materials and for heavy lifting. While originally created for this simple purpose, its abilities as a weapon were obviously underestimated, as Gordon Freeman
puts the Gravity Gun to considerable use in his fight with The Combine
, and indeed it can be said he is only so successful against their forces because of his use of the device.
The Zero-Point Energy Field Manipulator has two basic functions, "grab" and "punt." Gordon can grab objects, hold them, and then punt them with significant force while they're being held. This allows Gordon to effectively launch relatively heavy objects with a very high initial velocity, turning everyday objects into deadly projectiles. Gordon can additionally use the punting function of the device to move objects too heavy to be picked up normally and to destroy simple obstacles.
Dark Energy Field Manipulator
Initially, the Zero-Point Energy Field Manipulator is incapable of interacting with organic bodies larger than a simple headcrab
(which can only be punted, however, and not grabbed). During Gordon's time in the Combine Citadel
, he falls into a Weapon Confiscation Field, which immobilizes the being within the field, identifies all weapons carried by said entity, then strips the being of their weapons and incinerates them with Dark Energy -- the energy that powers the Combine's inter-dimensional portal. The Dark Energy has an adverse effect on the Gravity Gun, as it is powered by a nearly limitless source of energy - a zero-point energy field, which draws power directly from space-time - and imbues it with the ability to manipulate organic objects, as well as boosting the kinetic power of the Manipulator's standard grab and punt features. Using the Dark Energy Field Manipulator, Gordon can snatch and propel Combine soldiers, killing them instantly, as well as literally tear heavy equipment from the walls of the Citadel.