The madness of Malkavians
One of the many beautiful touches in Vampire: The Masquerade: Bloodlines is that picking the insane Malkavian clan for your character completely changes the game’s dialogue. Changes it into a mix of psychotic dementia and lucid insight - far beyond anything in the other character choices. It even afflicts your pet ghoul, a nice college girl called Heather, who takes to your blood like the finest drug, until the two of you are nattering like true psychotics, and the world is that much crazier.
Command & Cretaceous
While the original Command & Conquer suffered from really bad expansion packs, the first offered a particular entertaining secret. Adding the “funpark” parameter when running the game opened up a top secret set of five missions that pitted the standard armies of GDI and Nod against... dinosaurs. For no reason. There was even a briefing movie and bonus music track. And developers Westwood didn’t even mention it. The concept would later be copied by many developers, including Blizzard’s infamous Cow mission in Diablo 2.
