Tony Hawk's Project 8 Codes -

Play as Grim Reaper
Go to options, cheats, and enter the code "enterandwin" to unlock the grim reaper as a playable character.

Play as Travis Barker
Go to options, then cheat codes, then enter "plus44" as a cheat. If you entered it correctly, you should hear a noise.

Skate as Christian Hosoi
Enter hohohosoi as a code.

Skate as Dad and Skater Jam Kid
Enter strangefellows as a code.

Skate as et Colonel and Security Guard
Enter militarymen as a code.

Skate as bum
Enter enterandwin as a code.

Skate as nerd
Enter wearelosers as a code.

Skate as zombie
Enter suckstobedead as a code.

Skate as twin
Enter badverybad as a code.

All specials unlocked in the shop
Enter yougotitall as a code to unlock. Note: This does not include decks or pro tricks.

Almost all decks
Enter needaride as a code. All decks except for the Inkblot deck and Gamestop deck will be unlocked and free.

Inkblot deck
Enter birdhouse as a code.

Glitch: Play as a pro skater in career mode
Go to the training garage in the City Park. Select the pro skater you would like to play as in career mode then select any of the tutorials on their list. Once the tutorial starts, skate over to the two big garage doors that are on one side of the training room. One of the doors has a big arrow on the ground that is pointing towards it, and the other door has a big arrow on the ground that's pointing away from it. Stand on the arrow that's pointing towards one of the doors, and it should give you the option to leave. Use that to leave the training building, and you will appear in the City Park again as the pro skater.

Your tricks will not change to the pro skaters trick set, like they do in Free Skate mode. The tricks will remain the same as you had them set. Also, you will not be able to change anything on any of the pro skaters in your room (clothes, eye color, hair color, etc.).

The only way to change back to your other character is if you go to your room in Suburbia and recreate your skater. Before you can recreate your skater in your room, you will need to select one of the default looks so you aren't a pro skater any more (since you can't change anything on the pro skaters). Quitting the game without saving will not change you back into your other skater. If you do that you will still be the pro skater when you return to the game.