Arma 3 (on steam).
It's a military/survival game. If you like a mix of GTA V, H1Z1 and CS:GO, this is something for you.
Cheaters are instantly deleted from the serious servers. It is a 100% roleplay game.
You will talk and act as if you are in fact out on a field shooting people with your team mates.
For example, if you talk bad to your team mates, you will most likely be banned from server.
Takes a while to learn everything about the game, but it's probably my favorite game of all time.
If you're into roleplaying - I believe this is the most roleplaying & mature game you can find. It sometimes feel like you're in the army, out on duty.
A great server with awesome community: www.grandtheftarma.com
Tons of videos, but here is just a random one showing some of the roleplaying:
https://www.youtube.com/watch?v=SOaeObAfV9k