The game The Elder Scrolls V: Skyrim has a hidden chest that can only be accessed by exploiting a glitch in the game's programming.
In the game Halo 3, there is a hidden room that can only be accessed by crouching behind a specific wall on the level "The Covenant".
The game Assassin's Creed II has a hidden area in the game's credits where you can play as Desmond and use his abilities.
In the game Dead Space, there is a hidden room that can only be accessed by using a developer console.
The game Metal Gear Solid 3: Snake Eater has a secret ending that can only be unlocked by not moving during the game's opening cutscene.
In the game Portal, there is a secret cake recipe hidden in the game's files.
The game Batman: Arkham Asylum has a hidden room where you can see a map of the entire game world, including areas that are normally inaccessible.
In the game Half-Life 2, there is a hidden room that can only be accessed by turning on the console and entering a specific code.
The game Silent Hill 2 has a secret UFO ending that can only be unlocked by fulfilling certain conditions throughout the game.
In the game Super Mario Bros., if you wait for the game to idle on the title screen for a few minutes, Mario will go into a mini-game where he can collect lives.
In the game The Legend of Zelda: Ocarina of Time, there is a hidden room in the Temple of Time that can only be accessed by playing the Song of Time backwards.
The game BioShock has a secret room that can only be accessed by turning off the game's Vita-Chambers and dying in a specific area.
The classic arcade game Pac-Man has a kill screen on level 256, where the game becomes unplayable due to a programming error.
In the game Grand Theft Auto V, there is a hidden underwater hatch that leads to an alien spaceship.
In the game Animal Crossing, there is a secret room in the museum that can only be accessed by hacking the game. Inside the room, you can find a painting that is worth millions of bells.