DayZ, Arma 3 with BF4 coming in third place (minus the issues that are still beating around).
DayZ is just a ball to play with friends. I couldn't care less about having the best gear, I'm in it for the player interactions. Why, just today I challenged a random stranger to a fist fight. He played around before committing and got the first swing in. Knocked me out right quick. I woke up and he knocked me out again. Then he took my shirt, flashlight and battery (we were both new spawns) and took off. I woke up again, chased him down into a house and got knocked out again. Not to be discouraged, I woke up yet again and searched the village. He had taken off up the road, as I found out shortly thereafter. I caught up to him, and my buddy just happen to show up from the other direction. We beat him to a pulp, then I took my shirt back to tear into rags to bandage my cuts from fighting him. Then he got up again before my buddy could take his pants, so we found him again on the beach. Beat him down again and took his pants. Then a zombie chased us, and he happened to wake up as it was running by, thus grabbing the zombie's aggro and it killed him. That'll learn him to take my shirt!
Arma 3 just has so many mods like King of the Hill and Altis Life that are extremely fun. And it's great how detailed it is in regards to real life war-fighting.
BF4 is, well, BF4. I love the games minus the bugs/hit issues/etc.