Cheat: Unlockables and Tricks

Make Snake Hurl
Spin snake in circles while in the cure menu and Snake will throw up.

Create Your Own Title Screen
While viewing the title screen you can make it do a variety of cool tricks. L3 changes the pattern in the background, R1 speeds up action,  R2 slows it down,  L1 switches the black silhouette from the foreground to the background, L2 changes the color of the silhouette and finally,  L3 changes the color of the pattern in the background.

Unlockable: Monkey Mask
Earn the top 5 scores in Vs. Ape to unlock the monkey mask.

Unlockable: Nightmare Game
Following Snake being tortured, save the game. Load this save in another game, and you'll get a  sword fighting mini-game..

Beat the game to get:
Patriot with infinite ammo, Tuxedo, Camera, Single Action Army
 
Unlockable Camouflage
Beat the following using non-lethal force:
Ocelot: Animals – Steady aim
The Pain:: Hornet Stripe – Wards off insects
The Fear: Spider – Trades stealth for stamina
The Fury: Fire – Less damage from fire
Volgin: Cold War – Russians will not attack