PCCheats
Tony Hawk's Pro Skater 3

Walkthroughs and Guides
Outside link to all the information you'll need on this game, and more!
Courtesy of: Gamefaqs.com

PASSWORD CHEATS

CHEAT MODE PASSWORDS
Pause game play, then enter the cheats menu in the options screen.
Enter one of the following case-sensitive passwords to enable the effect you require

Effect .... Password
Master code .... backdoor
Level select .... roadtrip
Unlock all characters* .... YOHOMIES
Unlock all created skaters .... WeEatDirt
Unlock all decks .... GiveMeSomeWood
Unlock Doom Guy skater + Gearbox Tribute FMV sequence .... idkfa
Unlock all FMV sequences .... Peepshow

*Does not unlock Doom Guy

UNLOCK THE CHEAT MODE
This is an alternative way..
Play as usual then pause the game, hold fast spin left, then press up, grind without releasing the fast spin left button, then go to the menu, and select end run.

Submitted by: AJ and CheatBookJon