Ruthless realism for the ultimate immersion.
If I had to solely recommend one mod on this list to you, ACE 3 would be the one. It allows you to carry wounded teammates, adds shortcuts for placing and detonating explosives, adds proper bullet drop as well as shrapnel to explosions, it forces you to wear earplugs if you don’t want tinnitus from gunfire, and much much more. To name a few of its features ACE 3 integrates a complex, limb-based medical system, that allows you to for example address a specific bullet wound in the arm of a fellow soldier. This is a mod that is so deep that even Jacques Costaue would have trouble getting close to it.
The single greatest mod ever made for Arma III.