Retrieve the GECK for Arroyo

 is a quest in Fallout 2.

Background
This is the main starting quest given to the Chosen One at the beginning of Fallout 2.

Walkthrough
There are two GECKs in the game, One at Vault 13 and one at the Final Base.

In order to retrieve the GECK from Vault 13, there are three ways. Note that a possible bug prevents this route. At the Vault you will have to either negotiate with or dispose of the inhabitants, which will require the Vault-Tec Computer Voice Module, which can be obtained from Eldridge in New Reno Arms, or Vault 8 (in Vault City).
 * One must make his way to NCR, talk to Sheriff Dumont (standing on the corner in NCR Downtown), tell him you're looking for "honest work." He will then refer you to Westin (the entrance to his ranch is just to the west of the Sheriff). Your referral from the Sheriff (must pass karma check) will get the guard to open the gate. Take the quest to investigate raids on the brahmin and then track the perpetrators (talking deathclaws) back to Vault 13 (must have a high Outdoorsman skill to track them).
 * Talking to Saltbeef Bob (in the Westin Ranch compound) and giving him a drink of alcohol will get him to tell his yarn. This reveals that a doctor in NCR stole his map to Vault 13. Confronting the doctor gives you an option to buy his Velvet Elvis painting, which unknowingly to the doctor, contains the hidden map. You can then use your steal skill to get the money back (About 50% should allow you to do it).
 * Alternatively, take Tandi's quest to clear/negotiate with with the squatters in Vault 15, kill or leave Darion (your choice based on which quest you are doing) on Level 3. Opposite from his room is the computer room. One of the computers has information on Vault 13, although it requires a decent Science level.

Or, much simpler, just get to the Oil Rig. In the floor trap room, in the "safe room" all the way to the right, a GECK can be found in one of the lockers. You're missing out on a lot of XP if you choose this route, but you keep the deathclaws alive...until you talk to them again. However, Killap's faithful users can get around this.