This will only work on the PAL version of the game.
First make sure the game is set to 50hz (this is crucial).
If it's set to 60hz then take your memory card out before you boot up the game, set to 50 .. then re-insert at the title screen.
Anyway... just load up your game or start a new one.
In order to do the superjump you need to have a stick or a sword equipped (will also work with lightsaber).
Start running in any direction and do a running jump.
Right after you hit Triangle, hit Square. The timing needs to be really exact.
If executed properly you'll see him fly farther and one 'block' higher than he normally would.
Keep practicing the jump, it will come in handy when you'll need to get to Yorda quick.
....You can also skip major parts of the game with this jump, I won't tell you where... but just have fun with it, explore.
Contributed By: okita_san.
Enable 2 Player Mode
This code does not apply to the North American version of the game
Play and finish the game once, wait until the credit finish and once you get control of ICO, search for Yorda beside the sea shore. After the final ending you will be prompted a save screen. Save it and restart the game with Yorda controllable (2nd player) and 5 different background music / screen to choose from.
Contributed By: coldnet.
English Subtitles(PAL Version)
Upon completion of the game, not only do you get to control Yorda and have different music, but her subtitles are now in English rather than in hieroglyphics.
Contributed By: OrlandoReborn.
The game must already have been completed in order for this to work. Right at the end of the game when Ico wakes up on the beach, make your way all the way over to where the cliffs are and continue your way up the beach. Along the way you should come across a large rock, there should also be a couple of watermelons situated near this large rock. Pick up one of these watermelons and proceed up the beach until you reach Yorda. You will now be treated with a slightly humurous end video. This does not work on the US version of the game.
Contributed By: ~StickyBloodstains~.
Star Wars-Like Weapon
This code applies to any non-US version of the game only.
With 2 Player Mode enabled, play the game through the waterfall and reach an area where you get the mace by throwing a ball into a box at the first play (Please refer to FAQ for this side quest). This time a Starwars-like Weapon will fly in instead of mace.
This weapon is very powerful and will kill the shadow within 1-2 hits. And the weapon will be prolonged to triple the size of the sword if you grabbed Yorda's hand when attacking. (Even longer than the original Star Wars lightsaber)
Contributed By: coldnet.