$35 on Green Man Gaming
http://www.greenmangaming.com/s/us/en/pc/games/shooter/aliens-colonial-marines/
Key Features:
The most terrifying creature in cinema history
Face off against the ultimate enemy, as they use their unearthly skills to navigate across walls, swarm through vents and find new ways to attack you and your squad.
Enlist in the Marine Corps
Bringing you a true sequel to James Cameron’s classic Aliens, get tooled up with classic Marine weapons including pulse rifles, motion trackers and flamethrowers.
The most authentic Aliens experience ever
Using authentic environments inspired by the film series including Hadley’s Hope, the Sulaco and LV-426, you will be immersed in an eerie, atmospheric world where any moment could bring your death.
Drop-in / Drop-out co-operative gameplay
The masters of co-op bring their expertise to the Aliens universe. Xenos getting too tough? Call up your buddies so they can drop in with extra firepower. The whole campaign can be played with a squad of up to four players, dropping in and out as necessary through self-contained missions within an over-arching narrative.
Loadouts and upgrades
Create your perfect killing machine. An extensive upgrade system allows players to customise their characters to play the way they want. Earn experience to get perks, new weapons and new looks for your squad.