Apart from stealth games that allow for non-lethal attacks, unconsciousness is a bit of a rarity in games. And in Fallout 4, NPCs basically have two states: alive or dead. But sometimes you just want to knock someone out, especially while using fists or a non-lethal weapon. Thankfully, the Knockout Framework mod is here to sing Fallout 4's NPCs a violent yet soothing lullaby.
With the mod installed, you'll be able to knock out just about any NPC or creature in the game using your fists or gun-bashing. It's not an instant KO: the mod just determines when an NPC is about to be killed by a non-lethal weapon, and instead it renders them unconscious.
An unconscious NPC will remain in that state for a while (you can customize how long in the mod menu's options), and when you interact with their body you'll have some new options. You can choose to wake the unconscious person up, useful since your companions can now be knocked out during combat. Best of all, not only can you completely loot a knocked-out NPC as if they were dead, but you can also kidnap them and take them somewhere else.
Enjoyably, kidnapping an unconscious NPC places an enormous duffel bag on your character's back:
"Nothing to see here. Just carrying a giant sack around like a normal person who doesn't pummel people unconscious and then kidnap them. There's not a body in there or anything. It's just... my extra socks."
You can, naturally, remove the kidnap victim from the bag using your Pip-Boy at whatever location you've taken them to. Wake them up, dump them off a bridge, leave them looted and confused somewhere... just use your imagination.
The mod's author, Seb263, also has a companion mod, Non-Lethal Armory, that changes the behavior of a number of weapons. It's not required to make Knockout Framework function, but it'll give you more options for beating NPCs unconscious. The mod makes weapons like the tire iron, rolling pin, pool cue, baseball bat, baton, and several others non-lethal, allowing you to knock NPCs out with them. (And by the way, you can now be knocked out too, though NPCs can't kidnap you.)
You'll find Knockout Framework on Nexus Mods.