3) Batman: Arkham Asylum- Warden Sharp's Secret Room
In a game full of secret collectibles, you'd think players would have noticed that blowing up a certain unmarked wall would reveal Warden Quincy Sharp's super-secret private office. Inside, you see lockers, a desk, a statue of the warden. Standard office stuff. Except there are also blueprints and concept art on the wall showing that Sharp has bought land in downtown Gotham and plans to expand his asylum. This was included to drum up rumors about the game's sequel, Arkham City. Only the developers made this secret room so hard to find that no one actually discovered it before Arkham City was officially announced.
2) X-Men Origins: Wolverine / Just Cause 2- Dharma Hatches
It might only be a few years old, but like it or not LOST has firmly rooted itself into nerd culture everywhere. It's tendrils run so deep into the average nerd brain that it gave the designers of Wolverine and Just Cause 2, very different games, the same exact idea: "You know what's badass? LOST. What could I sneak into the game without my boss realizing? Oh, of course, a Dharma hatch!" In both games you chance upon each hatch randomly in the woods, and they're both immediately recognizable by the numbers on the outside. Now all that's left is confirming the rumors of playable polar bear skins and Hurley's secret buffet minigame.
1) The Legend of Zelda: A Link to the Past- Chris Houlihan's Secret Room
Legend says that in 1990, a boy named Chris Houlihan won a Nintendo Power sweepstakes to have his name featured in the newest Zelda game. Players later discovered that, through a series of well-timed dashes with the Pegasus Boots, Link can fall down a hole and into a room with 225 rupees. That's roughly equivalent to two red potions or the first question in Slumdog Millionnaire. There's also a plaque reading "My name is Chris Houlihan. This is my top secret room. Keep it between us, ok?" The real kicker is that no one actually knew this room existed until some dedicated Zelda nerds found it with an emulator in the past few years.
It just goes to show you, there's always a good reason to keep playing videogames, no matter what your family says.