Is it possible to kill everyone or are some NPCs unkillable?
Is it possible to kill every last person (and non-person) in Fallout New Vegas? Or are some NPCs unkillable?
Not that I would advocate or condone such a monstrous action, just idle curiosity.
Yes.
Unlike Fallout 3, no NPC's have 'plot armor' or are otherwise permanently flagged as 'Essential'. You can kill every NPC in the game according to the developers, save one. In fact, it was reported before release that one of the pre-release playtests consisted of a run through in which noone was spared. The final body count reportedly clocked in somewhere around 2500-3000 kills.
That said, there are, technically, 3 exceptions.
- The Gun Runners Vendor-Tron outside Freeside cannot be killed because he is behind a wall that cannot be passed without using the console to no-clip through. He is 'killable', but he is unreachable, rendering that fact moot. However, he is also a robot.
- Yes Man technically can not be killed. If killed he will simply respawn. This is explained in that he is not actually a specific Securitron, but rather a program (more like a virus really), that can run on any Securitron, and if the one which he currently inhabits is destroyed, he will just download into a new body. Yes Man is the 'only character that cannot be killed' that the devs bragged about, because he is required to trigger the final quest. If all other paths fail, 'Wild Card' is the fallback.
- Children, such as those found in Freeside, can not be harmed or killed, at all, ever.
I have not yet finished the game, but thus far I have killed (and eaten) every single person I have come across. While this course of action has resulted in many failed missions, it really is fun. I do plan on actually playing through the game once I finish my genocidal run as a madman named Eli (who looks surprisingly like Denzel Washington, right down to the sunglasses) who carries around a scorched pre-war book everywhere he goes.