8. Call of Duty - Black Ops: The Computer
The majority of the plot of the first Black Ops revolves around Alex Mason undergoing interrogation from the confines of a chair he remains strapped to. However, by tapping in a serious of actions (spacebar on the PC and a combination of back buttons on consoles), Mason will free himself from his bonds and is able to wander around the interrogation room. Once free, he can also access a computer terminal at the back of the room which accepts a number of commands including allowing the player to play a version of Zork, the famous text based game... This Easter egg not only requires the knowledge that you can break free but also of the layout of the server system of the terminal. The usually crass Call of Duty system has effectively called some of its critics back into the fold with a better game with a sturdy storyline but also with the inclusion of this small feature that is a fun diversion from the main shooting gallery event.