Insurgency is a great realistic warfare game that has a feeling of realism between Arma and matchmaking of Counter Strike. A great game for war realism.

Rust is a hard but fun open world survival game. Loot, collect recourses, grind for xp to craft better stuff, or pillage bases with c4.

Starbound, a fun 2D sanbox game that has a Terraria like feeling. Explore planets, fight dungeons. Play solo or play with a group of friends.

Arma 3 is a great game for serious platoon cooperation or silly life mod with friends. It is honestly one of the most realistic war games out there.

Unturned is a great yet simple game. Free to play, but don't let that fool you. Unturned is a Zombie apocolpyse where you can find gear and vehicles.

Payday2, Robbing banks, infiltrating warehouses and taking out the the bads guys. Alongside your 3 friends. One of the most fun squad games out there!

Do you like Brawling? Brawlhalla is a fast paced, learning, fighting type of game. Ranked, PVE fun for everyone. Pick characters and fight friends.

Do you like building? destroying? creating? Check out Garry's Mod, create new things play amazing gamemodes with your friends.

Competetive, yet fun. Team up with 4 friends and take to the competitive matches of CS:GO where people are down your throat, or complementing your skin!

Intense multiplayer gamemodes, fun to play with friends and more! Killing players to destroying robots and capturing objectives or points!