Strike Force: Desert Thunder [steam key]

http://store.steampowered.com/app/444210/Strike_Force_Desert_Thunder/

Strike Force: Desert Thunder is a small First-Person-Shooter game in the style of old, classic Delta Force games. You join 10 intense, large scale missions to prevent terrorist attacks. Customize your loadout, choose between 12 weapons and jump right into the action. Each Mission is large scale (2km²) and open to your tactical strategy.

Develop your own plan to attack the terrorists!