The Sniper Rifle CS-YippeeKiYay is a powerful bolt-action, realistic sniper rifle. This weapon fires bullets travelling at roughly twice the standard bullet speed of most weapons in the game, and inflicts a hefty damage on the target. Its name is a reference to the cowboy phrase "Yippee ki yay!". This weapon is manufactured by the Civil Security, due to the CS in its name. The Sniper Rifle was added into the game with the update Version 1.17 as a bonus weapon.
The Sniper Rifle CS-YippeeKiYay has some resemblance to the real life Dragunov sniper rifle, while retaining the sound of the Barrett .50 Cal, hence its menacing appearance. The barrel of the weapon is black, with a gray matte finish. This rifle is also equipped with a LED designator, indicating an enemy's presence when pointed toward them, regardless of whether the enemy is on the screen or not. It also comes with a laser sight attached, useful for precise aiming. The CS-YippeeKiYay can deal high damage, resulting in dying or death status in headshots especially, but also any area of the player.
There are major differences between the Sniper Rifle and the Railguns, which are also placed in slot 4. The Sniper is simply ballistic in nature, while the Railgun's projectile flight is near-instantaneous, the Sniper Rifle's ballistic projectile takes time to reach the intended target, and demands a high degree of accuracy on the part of the user. Additionally, the ballistic nature allows for applications that the railguns can not work for. The bullets can bounce, given the right angles, and also penetrate thin walls.
The Sniper Rifle's power is best described as being between that of the Lite Railgun and the Heavy Railgun. Three LED lights can be found on the side of the gun, and can determine the gun's status, such as reloading, or if it has spotted an enemy. When the gun is loading, the lights flash red, but when the gun is loaded and pointed at an enemy, the lights will flash green. This feature is great for targeting enemies off-screen. When the gun is loaded but not necessarily pointing at an enemy, it will glow a hazy turquoise color.
The Sniper Rifle CS-YippeeKiYay can be found and picked up in the campaign, but cannot be bought or upgraded in the equipment shop. The weapon is a rare sight in campaign levels, being found only on impossible difficulty, replacing Heavy Railguns and retaining their upgrade levels, other than the Heavy Railgun that Proxy can pick up in Level 30. A level 3 Sniper Rifle can be picked up and used in Level 40 when played on impossible, and added to the hero's arsenal.
- The laser will shake when the user is crouching, which decreases the potential accuracy of the gun, especially if the user is relying on the designator to snipe at enemies off-screen.
- The laser can detect Civil Security Ghosts, even though they are invisible.
- It resembles the SVD.
- If carefully zoomed in on a photo of the Sniper Rifle, a small 'F' on the design is noticed.
- The firing sound is the exact same sound as the Barret 50.Cal Sniper Rifle from Call Of Duty: Modern Warfare 2. The sound can be heard by clicking this link: 
- It has the highest projectile power of any bullet class weapon, and the second highest projectile power overall.