Zone Skins
Feiser Zone Skin - Unlock the Impact Campaign
Piranha Zone Skin - Unlock the Voltage Campaign
Qirex Zone Skin - Unlock the Voltage Campaign

Hidden Trophies
Deadly Momentum: Get eliminated in a race on Novice difficulty (blowing yourself up will not count)

Thanks for the Memory: Win a Race, Campaign or Online race with each HUD style variation (2097, 3, HD)

Sponge: Absorb 500 items

Mercenary: Get at least 500 loyalty points for each team

Gemini: Complete 20 two-player, split-screen races

Motion Master: Win a Campaign or Racebox race with the motion sensor option set to 'pitch and steering (Pilot Assist must be off, and D-Pads and Left Stick must not be used to obtain this trophy)

Bling Brigade: Complete an 8-player Online race