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, halfway through the heist the power might get cut, during this time, there's a small chance that the player may hear the iconic crying of the Witch from Left 4 Dead, the player can see her crying in a locked, inaccessible room.
Once the player looks at her, she suddenly appears at the door, face pressed against it and screams at the player, before quickly disappearing. Whoever the player is playing as, they will respond in shock.
Unknown if this still occurs in Payday 2.
NOTE The following video contains a screamer!