While most devs and/or publishers nowadays are more than happy to sell any unused content that may or may not pop up in in the development process as material for the super-duper-preorder-DCL-assrape-edition (game not included, only costs half as much as the game itself), there are a few titles that regularly have anything from concept art (SOMA) to easter eggs (Age of Mythology audio outtakes) to full-fledged short stories (Amnesia) hidden in them. Sometimes in rather obvious locations such as a neatly named "extras" folder, sometimes deeply buried within otherwise unacceptable or encoded game files.
Does Anon have a favorite example for this, or at least some other examples?