Cheat mode:
Enter "JPEARCE" as a name to unlock all robots, arenas, trophies, and 9,999,999 credits.

Use any arena in free play mode:
Highlight a locked arena that is directly next to a locked arena in free play mode. Press D-pad + X when moving towards the locked arena. If timed correctly, the previously locked arena will be playable.

Switch robots:
At the main menu, select "War Zone" and choose any robot. After winning a match, the game will display your upcoming opponent. Press Select + A to play as your opponent against the robot that you last defeated.

Play as Behemoth:
Win the Russian Rampage Cup to unlock Behemoth.

Play as Chaos 2:
Win the Robot Wars World Championship Tournament Cup to unlock Chaos 2.

Play as Firestorm:
Win The Hamburg Heavyweight Cup to unlock Firestorm.

Play as Hypnodisc:
Win the Flip Frenzy Tournament Cup as Chaos 2 to unlock Hypnodisc.

Play as Mortis:
Win the Liberty Lightweight Cup in the North America Arena with a bought lightweight class robot. Mortis can now be bought for 40,000 credits.

Play as Razor:
Win The Nerves Of Steel Cup to unlock Razor.

Play as Thor:
Win the Robot Wars Championship Cup to unlock Thor.

Extra credits:
Purchase cheap armor and weapons from the junkyard and add them to your spares. Save the game and return to the main menu. Then, return to the robot setup screen. Sell the armor and weapons to get full price for them.