Garden of Eden Creation Kit

The Garden of Eden Creation Kit (G.E.C.K.) is a terraforming device created by Future-Tec, a division of Vault-Tec Corporation, to ease the process of harnessing the post-nuclear wasteland for the Vault dwellers.

Characteristics
Created by Doctor Stanislaus Braun, the Kit exists in two variants. The basic kit is a less advanced, but more commonplace Kit that contains basic amenities needed to harness a Vault to establish a post-nuclear settlement. The advanced version is effectively unique matter recombinator designed to recombine matter into a fertile, virgin landscape. Both versions of the Kit have the appearance of a silver briefcase emblazoned with the letters "G.E.C.K.". The basic G.E.C.K. was supposed to be standard equipment for all Vaults.

Basic G.E.C.K.
According to Vault-Tec advertisements, the kit contains all the seeds, fertilizer, and other equipment (including a cold fusion power generator and a basic replicator) necessary to start a new settlement in a post-nuclear world after emerging from a Vault shelter. In practice, a G.E.C.K. contains a fertilizer system with a variety of food seeds, soil supplements, and chemicals that can fertilize arid wasteland (and possibly selected sections of the moon's surface pre-conditioned to accept the G.E.C.K.) into supporting farming. The GECK is intended to be "disassembled" over the course of its use to help build communities (for example, the cold fusion power source is intended to be used for main city power production), and so on. Anything else people need, they are meant to consult the How-To Books/Library of Congress/Encyclopedias in the G.E.C.K. holodisk library for more knowledge. The little pen flashlight is just the cherry on top.

The G.E.C.K.s were designed to be used relatively soon after the war, as the seeds and soil supplements they contained dated rather quickly. Furthermore, since the pre-War scientists had no idea how the post-nuclear world would look, the Kits were woefully out of tune with the post-nuclear world. However, if used by people with the necessary technical knowledge, the G.E.C.K. could be a powerful tool, especially if it was combined with the resources and infrastructure of a Vault. Fallout Bible 6: "1b. What may be suitable for planting in the present may not be suitable in 20 yrs. This is esp true I would think in the FO universe with its rather unstable ecosystem. I mean if one really wanted to be certain that what one was panting would grow the best thing to do would be to collect the seeds, spores etc from already growing food sources - these have a guaranteed fertilization rate. After all those corn seeds that were put in the GECK 50 yrs ago now have not sufficiently mutated to endure the new Wasteland (even in a "normal" ecosystem, the only strains of plant that survive are those that mutate). You're absolutely right. The GECK builders had no idea what the post-nuclear world would be like, and they had no real way to anticipate it, despite their "thorough tests" (it's doubtful they gave it much thought, to be honest, considering how badly organized the Safehouse project alone was, not to mention the experimental nature of the Vaults) - still, it seems as if the seeds present in the GECK were viable for Vault 8. Evolutionarily speaking using old seeds would be like reintroducing a species that may have gone extinct or at the very least one that is not as cutting edge in its evolution. ''You bet. And that's dangerous on so many levels! Wheee!'' '''Also, as far as How-to books, schematics, sand crete etc.. this seems a bit user heavy. That is a GECK is going to be utterly useless to those who cannot read, or don't have the raw materials to construct a force field, sand crete polymers etc.''' ''The GECK designers assumed that the Vault Dwellers would know how to read and how to operate various technologies present in the Vault - they didn't plan for tribals or other contingencies. They also didn't plan on the FEV getting released, or the fact the Vault Dwellers might be attacked by giant mutated scorpions or rats, either. On one hand, you could say they weren't too bright, and on the other hand, you could say they weren't prepared for the future of the human race to become an extended Post-Atomic Horror movie. Silly rabbits!'' '''1a. Wouldn't this [the seeds and soil supplements] date itself rather quickly?' Sure, but the government subcommittees sponsoring the research and the GECK contractors (Future-Tec) weren't really concerned about that. They were "relatively certain" the seeds would be viable in a post-nuclear environment. They had done "thorough tests," and "all conclusions point to this as being the best option." The GECKs are a miracle... a miracle that they work.''"

Other information provided by the G.E.C.K. includes basic force field schematics as well as info on how to make adobe-type buildings from the landscape (or create chemicals that can create "sand-crete" walls). Furthermore, the GECK contained codes that allowed the Vault to create more varieties of jumpsuits (and weatherproof gear) from their dispensers, which they could do anyway before the GECK. It's possible the GECK contained other codes that could unlock more functionality within the Vault computers that weren't initially available because they would jeopardize the survival of the Vault if they were used or scavenged (or else they would interfere with the Grand Experiment). The GECKs also allow the Vault inhabitants to disassemble sections of their Vault (or take extraneous systems from the Vault) to create new homes and defensive structures on the surface.

If chosen to receive a G.E.C.K., a Vault would be issued two standard G.E.C.K.s. Vault 8's extra G.E.C.K. got swapped (whether by accident or some nefarious scheme, this is not known) with Vault 13's surplus water chips that had been ordered as backups.

Matter recombinator
The unique Garden of Eden Creation Kit provided to Vault 87 is a device capable of radically altering the Wasteland and transforming dead, irradiated soil into viable land suitable for farming. It does so by collapsing all matter within its given radius and recombining it to form a living, fertile landscape

Fallout
Unimportant to the main plot, the GECK is merely mentioned in Vault Dweller's Survival Guide (Fallout's manual) in an advertisement describing the GECK's features.

Fallout 2
The GECK is supposed to be the miracle cure for the town of Arroyo, revered by the tribals as a pre-War artifact that can put an end to their drought. The reality is somewhat different than their expectations, as the GECK is a device that can help kickstart a settlement, though it requires trained hands to operate and ideally a Vault. Without it, the results can be less than stellar.

Opposite of Shady Sands is Vault City, founded with the GECK and Vault 8, resulting in the creation of an "utopia". The settlers of Shady Sands in 2122 also had a GECK, could not use their Vault as source of resources, meaning that the GECK could only help kickstart their agriculture and harness the land the hard way.

Fallout 3
The advanced G.E.C.K. is, as stated above, a matter recombinator and is a crucial component of an unspecified stage of the purification process in Project Purity. It is the objective of the Finding the Garden of Eden quest in the game. The player can activate the GECK, though in doing so, they trade the life of their character for a fertile wasteland.

Fallout 76
Vault 94 was issued one GECK for the purpose of recolonizing the Earth one year after the Great War. However, Vault 94 was also under the leadership of non-violent, faith-based commune which made them an easy target for the raiders of the Savage Divide. Vault 94 quickly fell to raiders who wanted nothing more than all their valuables. Once finding the GECK, however, the raiders were perplexed by the radiation it was giving off and decided to destroy it out of impatience. The resulting explosion would create The Mire region in Appalachia. The GECK wouldn't stop functioning after the explosion though and would continue to spew a massive amount of radiation for years to come.

Fallout Tactics 2 and Fallout: Brotherhood of Steel 2
Both of these games would include GECKs contaminated with radioactivity, causing them to create mutated flora and fauna that would consume massive areas of land and be central to the story, acting like the advanced GECK.

In Tactics 2, nothing is known about the GECK, as the game never left pre-production. The GECK in Brotherhood of Steel 2 was found by a former Jackal called Miles Reese.

Software Development Kit
The Fallout 3 SDK (Software Development Kit), called "The G.E.C.K.", has been released and is up for download at the official Fallout 3 website. It is also available for Fallout: New Vegas.

Behind the scenes

 * The G.E.C.K. was created by Jason Anderson and Leonard Boyarsky for the Fallout game manual as a flavor item. It wasn't intended to be used in a sequel. But as far as a McGuffin goes, it was there when it was needed.
 * The G.E.C.K. (or more precisely, its intended function in Fallout 3) might be a reference to the movies Star Trek: The Wrath of Khan and Star Trek: The Search for Spock, which revolve around "Project Genesis" and the Genesis Device. Like the variant of the G.E.C.K. encountered in Fallout 3, the Genesis Device is intended to be used to create life out of lifelessness (whilst killing every present living thing in its working radius upon activation).
 * There is no clarification from Bethesda on how to reconcile the two radically different views of the G.E.C.K. The view of the GECK as a miracle device is a far cry from the view of the GECK as a pretty useful piece of pre-War agricultural technology.