Ico

Hint: Destroying the Smoke Creatures easily:
If you enter a room, and it is a clear run to the portal on the other side, take Yorda by the hand and run her to the portal with the black Smoke Creatures chasing you. As you approach the portal, Yorda's activation of the portal will create lightning which will destroy the creatures anywhere near you.
Otter.

Hint: Finding Yorda:
When in the last level with Ico's horns cut off on the beach, go towards the left following the shore of the beach to find Yorda.
RoCaWeAr.

Hint: Avoid losing Yorda:
To avoid losing Yorda, as soon as you set her free press R1 and hold her hand, then run to the door . You should also pick up the stick that falls so you can defeat the Shadow Creatures easily.
Abax1616.

Hint: Share a watermelon with Yorda:
Ico can share a watermelon with Yorda at the very end of the game. Note: This was done on the second time through the PAL version of the game. Take Yorda one of the watermelons sitting in the sand dunes. They are also very satisfying to smash.
bryn.

Hint: Turning wheels:
When turning big wheels, as when shutting off the water, turn from the farthest point to go faster.
RoCaWeAr.

Hint: Mace weapon:
After reaching the top of the waterfall area, to the left of the switch you pulled is a tall tree. Swipe at it with your sword until you make contact. A ball will fall from its branches. Take the ball up the stairs, into the opened room, and drop it. You will notice tree arches between the two stairs going to the upper level of the room. Go to the middle arch and push on one side of it to make it revolve and reveal a secret room. Go back and take the ball (and Yorda) and enter the secret room . Hop into the idol pedestal with Yorda and a basket will appear. Take the ball and shoot it into the basket. A mace will fly through the window. It is more powerful then the sword and the 2x4. You can take out a standard Ghout in three swings.
Tunde Adelabu.

To get the Mace, you do not need to do the "get the ball in the basket" routine. Before getting on the idol pedestal, actually place the ball in the square on the ground, where the basket will appear. When you step on the idol pedestal, the ball will fly up and land back in the basket.
Ben Norton.

Hint: Lightsaber weapon:
Successfully complete the game once, then start another game. Follow the steps to where you got the Mace in the first time, and this time you will get a lightsaber that kills Smoke Creatures in one hit .You must be holding Yorda's hand to activate it.
tdj1.

Hint: Extra puzzle (PAL version):
An extra puzzle has been added in the room that leads to the top of the waterfall garden in the PAL version of the game. Whereas before you could shimmy around the room on bars, now you can only reach a switch. Pull this to start a giant wooden piston in the room. To get to the window, stand on the piston and press Jump just as it begins to sink to the lowest point. You should be catapulted up to a ledge. Just climb up to the window.
Ben Norton.

Hint: Two-player mode (PAL and Japanese NTSC versions):
Successfully complete the game and wait for the credits to end. Once you regain control of Ico, look for Yorda near the seashore. A save prompt will appear after the final ending. Save the game and restart to have Yorda playable using controller two and new music.

Hint: 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.
Ben Norton.