Venom Bike
If you want to race as Hotra Toxic with her super-fast Venom Bike, come in first on the Atomic Contest -- or, if you're too lazy, enter the following password: 868QCMH3H9HT.
Wasp Superbike
Looking for the second superbike? Finish the Contest Mode on Critical Mass difficulty, and you'll be able to drive the Wasp. You can also enter the following password:55Hz1MH3H9H1
Credit Goes To: Janitor Ed via IGN 64