During game play in Single player mode enter the following codes to unlock the corresponding effect.

Unlock Seasickness Mode:
Press X(x2), Y, X(x2), Y.

Unlock Ghost Form Mode
Press Y, X, Y, X, Y, X.

Restore Health:
Press Y(x2), Select, Left, Right, Left, Right, Left.

Restore Savvy:
Press X(x2), Select, Up, Down, Up, Down, Up.

Unlock Unlimited Power
Press Up(x2), Down(x2), Left, Right, Left, Right, L, R.

Unlock Invincibility:
Press Up, Down, Left, Right(x5), Left, Right, Up, Down, Left, Right, Up(x5), Left.

Gain 10 Gold:
Press Right, X(x2), Right, Left.

Unlock Silly Weapons:
Press Y(x2), X, Y(x3).

Unlock Slow Music:
Press Y, Select, X(x4).

Spawn Chicken:
Press Right, L(x2), Up, Down(x2).

Spawn Pig:
Press Right, R(x2), Down, Up(x2).

Spawn Axe:
Press Left, L(x2), Down(x2), Left, Up(x2), Down(x2).

Spawn Executioner Axe:
Press Right, L(x2), Up, Down, Up, Right(x2), Left(x2).

Spawn Pistol:
Press Down, L(x2), Down(x2), Right.

Spawn Blunderbuss:
Press Down, L(x2), Down(x3).

Spawn Rifle:
Press Left, L(x2), Up(x3).

Fast Music:
Press Y, Select, Y(x4).

Disable Cheats:
Press X(x6).