Metal Gear Solid 4: Guns of the Patriots/Unlockables

Secrets
There are many secrets to discover in MGS4, these are only a few, so feel free to add on any that you find!


 * Crop Circle- While tracking Naomi in Act 2, there is a path that leads to a small field, which contains a Crop Circle!


 * Water Treatment- While tracking Naomi in Act 2, there is a path that leads to a small concrete platform, where a PMC Soldier is urinating into the river.


 * Tailing Snake- In Act 3, while trailing the Resistance Member, you may see a figure following Snake. These are the Dwarf Gekko that you see in the cutscene after the Resistance Member leads you to the church.


 * Sunny's PSP- In Act 2 mission briefing you can see Sunny playing her PSP, the game she plays is Penguin Adventure, the first game of Hideo kojima.