Level Select:
At the main menu, press R1 + R2, L1 + L2, Circle,
Square.
After 1st Save All Levels Unlocked 800f7ad80002 800f7adc0006 Infinite Health 800feb7c0250 Infinite Health PT Boat 800feca017f0 Infinite Health Jeep 800ff80814b0 Infinite Health Tank 800ffa50ead0 Infinite Health Train 80100c901ff0 Infinite Grenades 800f89980909 Infinite Bazooka / Mortar 800f899a0909 Infinite Flamethrower / Auto Rifle 800f899c0909
Thanks to Revolution readers Tommy and Troy Tahtinen!