Get Perfect Balance:
After pausing the game hold L then press X, Left, Up, Right.

Unlimited Special:
After pausing the game hold L then press Left, Down, Y, B, Up, Left, Y, X.

Get 10X Points:
After pausing the game hold L then press X, B, B, Up, Down, Down.

Get 10X less Points:
After pausing the game hold L then press Up, Down, Up, B, B, X.

Get high Jumping:
After pausing the game hold L then press Up, Up, Up, Up.

Get Huge Tires:
After pausing the game hold L then press Down, B, B, Down.

Get Balance Display:
After pausing the game hold L then press left, B, X, Y, X, B, A.

Get Slo Mo Mode:
After pausing the game hold L then press X, Y, B, A.

Get Granny:
After pausing the game hold L then press Up, X, A, A, Down, B.

Get New Colors:
After pausing the game hold L then press Down, Down, Down, Down.

Get More Course time:
After pausing the game hold L then press X, Up, B, A.

Get Tony Hawk:
Get all 30 covers and 2 gold medals using any character in career mode

Get Burnside Level from Tony Hawk's Pro Skater Game:
Use all characters to get all 30 covers and 2 gold medals

Get Warehouse Level from Tony Hawk's Pro Skater Game:
Get a 200,000 point combo without using the cheats

Get Neversoft FMV:
Use Tony Hawk to get any medal on both competition levels

Get Grandma FMV:
Use Grandma to get any medal on both competition levels

All Special Moves:

Matt Hoffman:
down, down, B - Superman One-Hander
up, down, B - Backflip Tailwhip
left, right, X - Peacock
left, left, X - Barhop

Kevin Robinson:
down, down, B - Superman Tube Grab
right, right, X - Barhop

Mike Escamilla:
up, down, B - Backflip One-Footer
down, up, B - Front Flip
left, right, X - Body Varial
down, down, B - Superman Seatgrab Bar Spin

Cory Nastazio:
down, down, B - Superman Seatgrab
up, down, B - Backflip Tabletop
down, up, B - Front Flip

Joe Butcher Kowalski:
down, right, B - Half Barspin Tailwhip
down, down, B - Superman Backpeg Barspin
up, up, B - No-footed Candybar One Hander

Rick Thorne:
down, down, B - Double Seatgrab Superman
up, down, B - Backflip No Footer
left, right, B - Decade Air

Dennis McCoy:
down, down, B - Superman Tailwhip
up, down, B - Backflip One Footer
left, right, X - Decade Air

Tony Hawk:
down, down, B - Superman Tailwhip
down, up, B - Front Body Flip
left, right, X - Body Varial

Simon Tabron:
down, down, B - Double Seatgrab Superman
up, up, B - Superman Seatgrab
left, left, X - One-Handed Swing Leg
left, right, X - No-Footed Candybar One Hander