Faster Credits
After the Naughty Dog staff's names have disappeared off the screen, hold X or Circle. The credits will be shown at a much faster speed.
Faster Zoomer
Hold L1 and R1 to go faster on the Zoomer. This will make it less maneuverable, however.
Secret Ending
Get 100 or more power cells and finish the game to see a secret ending. If you get less than 100 power cells, you wont be able to see it.
Shoot Cannons Farther
The cannons at Misty Island and Sentinel Beach will shoot farther if you hold Square, or Circle and X.
Unlimited Health
Pause the game and press Up, Left, Left, Down, Right, X, and Triangle. Your health will not go below zero.
Very Powerful Attack
While punching, jump and you will do an uppercut. Then do a spin kick or a dive for a very powerful attack.