Non-Lethal or Lethal Resolution
Non-lethal or Lethal Resolution is an interesting mod that allows you to do exactly that: Take out your enemies permanently or, if you're feeling generous, temporarily.
With this mod active you can throw sleeping gas grenades, flashbangs, or mustard gas at your enemies to knock them out for a short duration. Flashbangs disorient them for a few seconds, the gas will incapacitate them for a few minutes.
You can also use melee weapons to knockout your enemies and there's also an M9 Tranquilizer gun that shoots darts that'll knock your adversaries out.
The developer is working to improve the mod with several new features planned and we're excited to see how this Fallout 4 mod evolves over time.