Tony Hawk's Proving Ground Codes -

Cheat mode:
Successfully complete Story mode by beating all the pro challenges and Tony Hawk's final challenge. You can now buy any of the following cheat options in the Skate Lounge for $1,000 each.

First Person Cam: Skate in first person view. 
Giant Mode: Huge skaters. 
Tiny Mode: Tiny skaters. 
Matrix Mode: Slow down time during ollies/air. 
Super Jump: Ollie higher, except off halfpipes and quarterpipes. 
Mirror Mode: Mirrored levels. 
Unrestrained Aggro: Easier timing for Aggro Kicks. 
Perfect Balance: Perfect Rail/Manual/Lip balance. 
Replay Camera: Skate with replay camera. 
Ice Mode: Visual: Bluish levels. 
Night Mode: Visual: Skate at night. 
Old Timey Mode: Visual: Film overlay graphics. 
World Of Darkness: Visual: Darker than night. 
Steel World: Visual: Dark graphics. 
Light Inversion: Visual: Shadows turn to light. 

Bonus skaters:
Enter the Skate Lounge and select "Change Gear". You can now access the following skaters after they are unlocked during game play for for $2,000.

Hippie 
Santa Clause 
Easter Bunny 
Zombie 
Robot 
Ninja