Button Combination Cheats:
Pause your game, hold down the L trigger, and then press the following buttons.

C-up, Down, Left, C-left, C-down, C-up, C-right - Slow Motion
Left, C-right, Right, Down, C-down, Up, Up - Simulation Mode
Down, Left, C-up, C-down, C-left, Right, Up - Super Turbo Mode
C-down, Right, Down, C-left, C-down, C-up, C-right, C-left - Perfect Balance
C-down, C-right, C-right, C-up, Up, Down, Right, Left - All Skater Stats at 13
C-down, C-left, C-right, C-left, Up, C-down, Down, Right, C-down, C-down - Double Moon Physics
C-left, C-down, C-up, Right, C-right, Right - Infinite Special Meter
Down, Up, C-up, C-left, Down, Up, C-up - Make All Skater Stats 10
Left, C-right, Right, Down, C-down, Up, Up - Thin Skater
C-left, C-down, C-up, Down, Up, Right - Turbo Mode
C-up, Down, Left, C-left, C-down, C-up, C-right - Slow-Nic Mode
C-down(4x), C-left, C-right, right. - 10x Multiplier (Always special)
C-down, C-left, C-right, C-left, Up, C-down, Down, Right, C-down(2x) - Physics

Unlockable Characters:
Here are methods on how to unlock secret and special characters.

Spiderman - Beat the game 100% with a created player to open up a playable Spiderman.

80s Tony Hawk - Beat the game 100% with Tony Hawk, (i.e. all objectives, 3 gold medals) to unlock a third style for Tony Hawk, called 80's Tony Hawk. Tony now has long blonde hair, and old-fashioned clothes.

Officer Dick - Beat the game 100% with all skaters. (Spidey and Custom included)

Game Completion Rewards:
Special codes and cheats that unlock only once you beat the game meeting certain criteria.

Hoffman Bike Headquarters Level - Beat the game with everyone and instead of unlocking Skate Heaven, you'll unlock the Hoffman Bike Headquarters from Mat Hoffman's Pro BMX. The outside area has been removed and the transfers (gaps) are no longer there. Its more of a fun course.

Skip to Restart - Beat the game with Bucky Lasek

Always Special - Beat the game 100% for the fifth time to unlock Always Special mode

Kid Mode - Beat the game 100% for the third time to unlock Kid mode.

Perfect Balance - Beat the game 100% for the fourth time.

Disco Mode - Beat the game 100% with Officer Dick to unlock Disco Mode.

Hidden Videos:
Video of Tony Hawk skating - Complete career mode with Tony Hawk
Video of Jamie Thomas skating - Complete career mode with Jamie Thomas
Video of Elissa Steamer skating - Complete career mode with Elissa Steamer
Video of Geoff Rowley skating - Complete career mode with Geoff Rowley
Video of Andrew Reynolds skating - Complete career mode with Andrew Reynolds
Video of Chad Muska skating - Complete career mode with Chad Muska
Video of Rodney Mullen skating - Complete career mode with Rodney Mullen
Video of Bucky Lasek skating - Complete career mode with Buckey Lasek
Video of Eric Koston skating - Complete career mode with Eric Kosten
Video of Rune Glifberg skating - Complete career mode with Rune Glifberg
Video of Kareem Campbell skating - Complete career mode with Kareem Campbell
Video of Steve Caballero skating - Complete career mode with Steve Caballero
Video of Bob Burnquist skating - Complete career mode with Bob Burnquist

Unlock Secret Courses:
Beat the game 100% with every character, including custom skaters and hidden skaters, and you will unlock the secret course skater heaven. If you beat the game with three gold medals, including custom and hidden skaters, you will unlock a course from a BMX biking game.

Marsellies France Secret Area:
To get to a secret area with tons of cash, skate around the grassy area until you hit a piece of glass. Then a hole will open in a wall.

Hangar Secret Area:
Simply grind the propeller above the Half-pipe to get to a wind tunnel area in the hangar.