Omikron: The Nomad Soul

An Adventure Video Game created by French studio Quantic Dream. Yes, that's the one behind Fahrenheit (2005 video game) and Heavy Rain, and is a game often forgotten to be mentioned in previews, reviews and discussions about Heavy Rain and Quantic Dream's work, which is unwarranted.

The plot concerns you, or more specifically, your soul. You buy a video game that allows your soul to enter another world; the titular city of Omikron.

Said city is a terrifying Dystopia where all human activity is planned by a monolithic super computer named Ix. Ultimately, the player finds out that the reason they are in the city is... well... not what they initially expected. The plot has players go from working for the government to working with a terrorist group to ultimately working their way though a Government Conspiracy that shows The Man Behind the Man is quite horrifying.

A Genre Busting game that incorporates fighting, FPS and RPG elements alongside its adventure, Quantic Dream call the game a "Soul Playing Game".

Tropes used in Omikron: The Nomad Soul include:

A.I. Is a Crapshoot: Ix.
Another Dimension
Beneath the Earth: You eventually find your way down to Omikron's spacious catacombs.
- Ancient Tomb
City of Canals: Lahoreh, one of the districts of Omikron.
Cool Sword: Barkaya'l, which is empowered by the souls of all the ancient sorcerers of Omikron (minus one), and as such is the only weapon powerful enough to kill the Big Bad.
Cyberpunk: Omikron.
David Bowie: Provides the soundtrack, alongside regular Bowie collaborator Reeves Gabrels; several of the songs would appear on his album hours.... He also plays TWO characters, who both have his polygonal likeness.
Decoy Protagonist: Sayl. He's played up in promotional material as the main character, with the intro showing him involved in sequences that come long after his death.
Dialogue Tree
Domed Hometown: Omikron, to protect it from an ice age that has engulfed the planet.
Dug Too Deep: While digging the foundations of Ix's palace, the construction workers accidentally unearthed the cage where the Big Bad was imprisoned, thus allowing it to extend its influence upon the world once again.
Dystopia: Omikron.
First-Person Shooter: Some segments of the game are played as an FPS.
Government Conspiracy: Omikron and every organization within it (apart from the terrorist group) are controlled by malevolent demons; the king of whom wants to torture your soul for eternity in order to fuel his attempt at mulitverse-conquest. The trusts, Ix and Legatee Reshev are all their puppets.
Irrelevant Importance
Justified Save Point: Magic rings with the ability to preserve your soul.
- Save Game Limits: You need to gather said rings.
Last Fertile Region: Jahangir Park.
Mega Corp: The government-linked trusts, Khonsu and Tetra.
No Fourth Wall: One of the earliest examples of this trope in video games. The game begins with a police officer from another world asking you to transfer your soul into his body. It only gets more demented from there.
Optional Sexual Encounter: Once near the start of the game.
Pamphlet Shelf
Peace and Love Incorporated: The Omikron government, which uses thought modifiers.
Place Beyond Time: You visit one.
Player Headquarters: They get changed a couple of times.
Point of No Return: Be sure to stock up before going on the path to confront the Big Bad.
Red Light District: Qalisar.
RPG Elements: The game includes fighting, First-Person Shooter and Adventure segments, with skill at all these segments being determined by the stats of the body you are currently inhabiting.
Save Both Worlds: Both Omikron and the real world!
Soul Jar: The player's soul may inhabit the body of several characters. Also, Barkaya'l.
Take Up My Sword: How you obtain the Cool Sword.
Tome of Eldritch Lore: The Book of Nout.
Urban Segregation: The city of Omikron is divided into four districts, each with its own style of architecture and fashion. People aren't allowed to move freely between them, they need special passes to do so. Only three of the districts are visited during the game.
Wide Open Sandbox: An early 3D example, you can explore the city of Omikron freely between (and often also during) missions: buy some stuff, read books, listen to music...