Games like Insurgency
Squad
Squad is a large scale combined arms multiplayer first-person shooter emphasizing combat realism through communication, team play, emphasizing strong squad cohesion mechanics as well as larger-scale coordination, tactics, and planning. It features 20 large open maps, vehicle-based combined arms gameplay, and player-constructed bases to create a heart-thumping, visceral gaming experience with split-second decision-making in real-world scale firefights.
Project Reality 2
Project Reality contains some of the deepest cooperative gameplay seen in video games today and is designed to promote both technical realism and teamwork without sacrificing accessibility in doing so. The result is a virtual battlefield that continually proves itself to be both enjoyable and intense to all manner of players, whether they be military enthusiasts or gamers looking to experience an intense and challenging firefight with friends where teamwork is just as important as a quick trigger-finger.
Arma 3
Arma 3 is a truly massive military simulation sandbox game. It offers a wide variety of true/sci-fi combat situations in both singleplayer and multiplayer modes. It also comes out of the box with a very powerful editor that allows players to create their own scenarios, campaigns and mapmodes both for single- and multiplayer use.
Enemy Front
You’re Robert Hawkins, an American stuck deep in Nazi controlled territory during the height of WWII. It’s up to you whether to fight your enemies face to face, snipe them from afar, or sneak past and sabotage their positions. Join the fight against the evil Third Reich in open-ended missions across war torn Europe.
Battlefield 2
In Battlefield 2, players will choose to fight for one of three military superpowers: the United States, the Chinese, or the newly formed Middle East Coalition. Armed with the latest modern weaponry, players can take control of any of the game’s 30+ vehicles to engage in major conflicts with over 64 players in some of the largest online battles on the PC. Additionally, persistent character growth allows players to rise through the ranks and attain the ultimate rank of General.
Counter-Strike
Play the world's number 1 online action game. Engage in an incredibly realistic brand of terrorist warfare in this wildly popular team-based game. Ally with teammates to complete strategic missions. Take out enemy sites. Rescue hostages. Your role affects your team's success. Your team's success affects your role.
Breach & Clear
Breach & Clear brings deep tactical strategy simulation to PC, Mac and Linux! Build your Special Operations team, plan and execute advanced missions, and own every angle. Choose your real-world squad -- US Army Rangers, Germany's KSK, Canada’s JTF2, UK SAS, and more -- and take on a variety of foes with different skill-sets and abilities. Learn to approach, engage, and dominate your opponents through superior tactics and training.
Rogue Warrior
Rogue Warrior is a character-driven, first-person-shooter, featuring Richard Demo Dick Marcinko's explosive personality in an action-packed single player campaign, and intense multiplayer combat.
Tom Clancy's Ghost Recon
The Red Army is back. Now that Russia's government has collapsed, a hardline leader is bent on taking over the republics. Enter Ghost Recon, an advanced, futuristic squad of U.S. Army soldiers. Unlike previous Rainbow Six games, the setting is much more focused on the military instead of anti-terrorist maneuvers. Next-generation inventory and weapons will give players a glimpse into the real U.S. Army "Land Warrior" program on which Ghost Recon is based.
Global Operations
Global Operations is a first-person tactical shooter computer game developed by Barking Dog Studios and published by both Crave Entertainment and Electronic Arts. It was released in March 2002. (Wikipedia)