Beat story mode with Knuckle Breaker. Then, defeat the Phantom-Blade car in the next challenge to the Phantom-Blade vehicle selectable.
Vise Intruder car
Beat story mode with Max Breaker. Then, defeat the Vise Intruder car in the next challenge to make the Vise Intruder vehicle selectable.
Ray Stinger car
Beat story mode with Fire Stinger and wait until the ending sequence is completed. Then, restart the game and select the option under "Continue" to start a Ray Stinger versus Fire Stinger challenge. Now defeat the Ray Stinger to make the Ray Stinger vehicle selectable.
Secret mode two option
Beat story mode with Berkaiser (Eisen Wolf). Then, a secret mode two selection will appear under the continue option. Beat this new option to unlock the last two Berkaisers (Eisen Wolves).
Beat level six in story mode, move the pointer to the upper right corner, and select that location.