Nimble in Stalker 2. In Search of a Guide

You can find Nimble in the Snork Cave in the southeastern part of Zaton, and you will get there during the story mission "In Search of a Guide". To start this mission, complete the previous quest "Like moths to a flame". As part of this mission, you will be able to get to the Clear Sky base, where Faust is supposedly hiding. But to do this, you need to find a guide, who will turn out to be Nimble.

Talk to Richter in Skadovsk or Shevchenko in Zaton (it does not matter) to learn about the secret base, and he will offer to meet the Hunter. Head southeast from Skadovsk or east from Shevchenko to meet the NPC. After talking to the Hunter, you will learn about the Snork Cave, in which Nimble is hiding.

Kill or spare Nimble?

Once you find Nimble, a short cutscene will play. Both characters will run away from the snorks and avoid the blast wave. Once you deal with the snork, you will have a choice — kill or spare Nimble.

What happens if you kill Nimble

If you plan to kill Nimble, you can loot his corpse to get Professor Kalanchi's map, as well as other items such as ammo and a PDA.

What happens if you spare Nimble

If you decide to spare Nimble, he will tell you more about Clear Sky, Faust's location, and navigating the base. You will still get Professor Kalanchi's map, as well as coupons (depending on the difficulty of the game). You can still shoot him after this, but you will not find anything useful on the corpse.

So which choice is better?

The best choice is to spare Nimble, as you will get coupons and more information about Clear Sky. He'll also teach you how to disable psi-beacons and tell you where to find Faust. You can still pick up the dropped weapon, so it's not worth killing Nimble for it.

I killed Nimble on my first playthrough, and it didn't affect the story at all. You might be able to meet him if you spare him in the snork cave.