Sniper Elite is a long running intense sniper game where you head to intense and distinct locations during war to tackle problems that others can't. There are many historic campaigns, insane X-Ray attacks and some rather interactive open environments to explore. Choose how you tackle situations and be prepared to deploy various tools. There's a fun spin-off where you battle the undead as well in a cooperative group, it's awesome. This is called the Zombie Army, with various entries.