Go to the Inventory screen and press L1, Triangle, R2, L2, L2, R2, Circle, L1. Voila!
Level Skip (U.S. version):
Go to the Inventory screen and press L2, R2, L1, Circle, Triangle, L1, R2, L2. When you return to the game, you've beaten the level (you big cheater).
Level Skip (PAL Version):
Go to the Inventory Screen and press: L2, R2, Triangle, L1, L1, Circle, R2, L2.. Now go beat the game already.
Not cheats, but cool anyway:
When climbing up a ledge, hold the walk button to do a handstand.
To dive - Hold the walk button and do a forward jump into water. Another thing you can do is do a dive on land and you will go into a forward roll.
Thanks to Revolution readers Brad Shaw, Aridia Twombly, Ivor Morris, Christina Harris, Jumbo, Charlie Grady, Brad Shaw, Daniel Ross, Eric Read, and Chad Morris!