All racers:
At the title screen, press R2, R2, R2, L1, Triangle, L2, L2, L2, R1, Square.

Bus!:
Beat the bus in Faceoff  number 4 to unlock it.

Face off Mode:
Beat championship mode once to open "Face Off" mode against the Roadster.

Get Tow Truck:
Beat the Tow Truck in Faceoff  number 2 to unlock it.

Roadster:
Beat the Roadster in Faceoff mode to unlock it.

Saloon GT:
Beat the Saloon GT in Faceoff  number 3 to unlock it.