When working on a career on Hard or Very Hard modes, there are keys at weapon points in hard to reach places. Most arenas in the career have a key which unlocks a cheat or arena. VCL Coliseum 2 and Park Hill arenas are secured in this fashion. Cheats for Secret Combos, Unlimited Hover Mode, Unlimited Ammo, Unlimited Energy, & Start With No Health are also secured by getting the keys.
Turn on your PS2 Without a disk inserted. Select System Configuiration and set the date to 12/25, A.K.A christmas and all racers will be wearing Santa Hats.
Hold L1 And Press X, X, Square
Note: This combo takes no energy and does not require the secret combo cheat
Note: You need the secret combo cheat to use this combo
Hold L1 and press Triangle, Square, Triangle, Square. Doing this multiple times will make the shield last longer then after a period of time the shield will disappear but there will be little stars around the vehicle this combo uses no energy.
Turn on the Playstation 2 without a game disk inside and then select "System Configuration". Now set the date to 12/25, and then put in the game disk. If done correctly, all racers will be wearing Santa hats.
To unlock Buzzsaw as a playable character, beat the Deathmatch, Endurance, and Eliminator modes with the same character on either Hard or Very Hard Difficulty.
It can also be unlocked on Normal.