Payday - The Witch

The PAYDAY series is a co-op first person shooter made by Overkill Software, the game itself is not a horror by any means, but the developers have put in a few hidden screamer easter eggs in their games.

No Mercy - The Witch
In July 2012, a new heist was added to the game which takes place in the No Mercy Hospital from the Left 4 Dead series. The power could be cut halfway through the raid. During this time, there is a small chance the player will hear the iconic crying of the witch from Left 4 Dead, the player may see her crying in a locked, inaccessible room. When the player looks at her, she suddenly appears at the door, her face pressed against it and yells at the player before she quickly disappears. Whoever the player is playing will be shocked. Not known if this still occurs on Payday 2.

Preview
NOTE The following video contains a screamer!
 * youtube.com/watch?v=qLBr3vU-6UE