A free mod for Fallout 4, by shavkacagarikia.
It's easy to see why this is one of the most popular mods for the game. The idea is simple: add a damage threshold to every weapon in the game, and make sure that every time you fire a weapon, you only lose the amount of damage that is equal to or less than the threshold. There is a lot of freedom in the way you can implement this.
The best thing about this mod is that it doesn't require any kind of patching, and it works with all kinds of weapons. It doesn't matter if you use a weapon from the game or you create your own, you don't need to worry about any kind of compatibility issues, and you don't need to worry about creating or using any kind of ammunition.
