The Metal Gear series is pretty famous for being gonzo-meta with it's easter eggs and extras. Take this one for instance. To get the 'Hideo Kojima' achievement in Metal Gear Solid: Peace Walker HD, you have to recruit Hideo Kojima, the lead designer of the entire Metal Gear series.
When you're infiltrating the Crater Base, there will be this really cool comic book style interactive bit where you play "Guess Which Truck Has the Nuke!". Each truck has their own Easter egg, but the third from the right is the one you're after. Choose that, and Kojima-san will join your cause.
- Xbox 360: 10G
- PlayStation 3: Bronze trophy