Silent Hills (lost build of cancelled sequel to "Silent Hill" horror game series; 2015)
Silent Hills was a cancelled horror game, meant as a new installment of the Silent Hill series. The game was announced back in 2012, alongside Policenauts and various other games, and was going to use the Fox Engine. On August 12th, 2014, a teaser game entitled "P.T" (an abbreviation of "Playable Teaser") was released on the PlayStation Store, under the pseudonym 7780s Studio. It was later revealed at the end of the game as the official teaser for a new Silent Hill game.
In 2012, game director Hideo Kojima announced that he and his studio, Kojima Productions, were currently working on a game with prominent figures such as film director Guillermo del Toro and actor Norman Reedus. The demo released in 2014 featured the player wandering around a strange house with no immediate references to Silent Hill. As the player traverses through the game, many odd and frightening events start to unravel, such as strange cryptic dialogue, the player appearing in the same rooms, the spirit of a pregnant female named Lisa that attacks you, etc. After completing the game, the player sees the protagonist wake up in Silent Hill, with the title card "Silent Hills" appearing afterwards. The demo was well received by many, accumulating an overwhelming amount of positive feedback. One reviewer claimed that he only lasted 30 minutes because of the "sheer level of directorial and artistic ambition" that the game had. 
In 2015, Hideo Kojima was laid off from Konami by the end of the year, which left the fate of the game's future uncertain. Later that year, the game's co-director announced that the project was cancelled. Unfortunately, the demo was removed from the PlayStation Store.  Footage of the demo can be easily found on the internet, as many popular YouTubers covered the demo before the project was scrapped. It was also rumored that Konami also destroyed many of the last known copies of the demo after the project was shelved. Kojima left the studio permanently.
Around September 2014, film director Guillermo del Toro made a video in regards to P.T.'s reveal and Silent Hills' cancellation. In this video, he reveals that the version of P.T. that was presented to him was in fact radically different from the one that Kojima Productions released onto the PlayStation Store. 
"To collaborate with a master storyteller like Kojima was irresistible. For concepts, we talked about tools, we talked about many things in his headquarters in Tokyo. And then he sent me the first version of his playable teaser, which was very different from the one you played now."
Alongside this, a concept trailer was released at TGS 2014, which could've been from the prototype build. There is, however, a lack of information surrounding this build, making this hard to confirm.
What makes this cancellation exceptionally different from most others is what happened behind the scenes, before and after Kojima was laid off. According to GamesRadar+ journalist Sam Prell, Kojima's last day at Konami was on October 9th, 2015, followed with a non-compete that was active until the end of December. Alongside that, Kojima was prohibited from appearing at the Games Award Show because he was "locked in a room for the final six months of Metal Gear Solid V".
Many have speculated that the cancellation was premeditated due to an internal feud between Konami's executives and Kojima (alongside his staff). YouTuber TheGrateDebate made a video detailing the events leading up to Silent Hills' cancellation, compiling and uncovering a lot of important information following the time between 2011-2015, and Kojima's departure from Konami.
- Silent Hill (Partially found graphic novel adaptation of horror game; 1999)
- Silent Hill: Cold Heart (lost rejected pitch from horror game; 2007)
- Martin Robinson. "Policenauts, Silent Hill and a Metal Gear JRPG - an audience with Kojima". Eurogamer. Retrieved 19 Sept '19
- David Houghton. "P.T. is still the purest horror game around, and one of the smartest on PS4". Gamesradar+. Retrieved 19 Sept '19
- GameSpot article on the cancellation of Silent Hills, which Konami confirms. Retrieved 07 Jun '15
- Polygon's article on the P.T. demo getting pulled from the PlayStation store. Retrieved 10 Nov '18
- "Silent Hills - Message from Guillermo del Toro TGS 2014 Trailer [HD 1080P"]. YouTube. Retrieved 19 Sept '19
- Sam Prell. "Report: Kojimas last Konami day was Oct. 9, non-compete active until Dec." GamesRadar+. Retrieved 19 Sept '19
- "Hideo Kojima Banned from Attending The Game Awards by Konami". GameRant. Retrieved 19 Sept '19
- Kirk McKeand. "Kojima was “locked in a separate room for the final six months” of MGSV, says Geoff Keighley". PCGamesN. Retrieved 19 Sept '19