11. Assassin's Creed III's Turkey Assassin
https://www.youtube.com/watch?v=OVDAfuryDks Here's one so obscure and so random, surely nobody figured it out until some seeds were planted by Ubisoft themselves online. Basically, in AC III you'll be slowly compiling your Homestead with various materials and buildings - but it's resting against a specific wall and whistling that'll attract a turkey to your side. From there you then need to input the legendary 'Konami code' (up, up, down, down, left, right, left, right, B, A) that's been used in more games you can count, and the turkey itself will sprout a tiny assassin's hood. Sadly he doesn't have any turkey-specific assassinations, but give Ubisoft time - it was probably floated as DLC at some point.