Bones Air Strike:
Pause game play & press Down, Up, Circle, Down, Up, Down, L1.

Cow Strike:
Pause game play & press Up, Down, Down, L1, Right.

Super Chain Gun:
Pause game play & press Left, L1, Down, Square, Triangle, Up, Down.

Thumper Weapon:
Pause game play & press Down, Up, Left, Left, Triangle, Up, Right, Down.

Twister Weapon:
Pause game play & press Down, L1, Square, Triangle, Right, Up, X.

Hand Grenade:
Pause game play & press Triangle, Circle, Square, Square, L1, Right.

Sniper Grenade:
Pause game play & press Up, Square, L1, Left, Circle, Triangle, Square.

Homing Sniper Grenade:
Pause game play & press Left, Up, X, Square (or Triangle), L1, L1, Right.

Mortar:
Pause game play & press Left, L1, Triangle, Square, Right, Circle, Left, Left.

Most Interesting Bomb:
Pause game play & press Down, Right, Circle, Circle, Left, Left, Up, Square, Triangle.

Dummy Decoy:
Pause game play & press X, L1, Right, Circle, X, Up, Square.

Bonus Arena:
In World 1 Arena 1, after you have blown up the atomic door with the 'world's smallest atomic device', turn around and go back to the original cave at the start of the game. You will find a shimmering pink ball. Step into the ball. You will appear in a new arena. Shoot all the Grunts in this arena. A tornado (useful for killing everything in an arena) and health bites will float down. Pick up these goodies and then step back into the ball. You will arrive back into the original cave and continue onward to Arena 2.

Level Select:
At the title screen press Left, Circle, Triangle, Up, Square.