16. Playable 1980's Zork (Black Ops)
Remember how awesome Black Ops was? The mystery around who was interrogating you, what the numbers meant, who you really were and what was really going on? That end twist still resonates to this day, and doesn't get anywhere near enough credit for how well it was all pulled off. Anyway, something that proves any developer is firing on all cylinders is to take note of how well done or secretive their easter eggs/references are aside from the base game. Paying tribute to Activision's 1977 original Zork, you can access it in all its text-based glory after you get out the torture chair on the main title screen. Simply look down (whilst still on the menu) and hammer the shoulder buttons to break free, then set about exploring the level. Log into the terminal computer and type either 'Zork' or 'Hello sailor' (a phrase used in the original game), and you'll then have to figure out how to progress, reading the descriptions and responding with prompts like "Climb", "Go", "Look" and more. Just take note - this was the highlight of narrative world-building back then, a far-cry from the likes of Skyrim, Metal Gear Solid or The Witcher 3, that's for sure.