When creating a robot, name it GLADIATOR to unlock all the arenas and arena editor. You can make a grand total of 3 arenas but can't unlock anything in them!
When creating a robot, name it SCRAP METAL. You then have unlocked all the parts except the Gold Parts. You still have to unlock all the trophies though!
When creating a Robot, name it HARD CASE and it will become invincible. It can still lose falling into the pit though!
When creating a robot, name it CONVERSE to unlock the All Star robots.