Controller debug:
Hold X + Y + Z + L + R at the main menu screen until the phrase "Info Mode: On" appears. Debug information will appear at the top of the screen during game play.

Invincibility:
Pause game play and press X, Z(2), X, Y, X, Y, Z, Y.

All weapons:
Pause game play and press Z, X(2), Z, Y, Z, Y, X, Y.

Level select:
Press X, Y, Z(2), Y, X, Y, Z, Y at the main options screen.

No monsters:
Pause game play and press Z(2), X(2), Y, X, Y, X, Z at the skill level selection screen. A new "No Monster" skill level will become selectable.

Death Tank Zwei mini-game:
Save a game from Quake or Powerslave onto the Saturn's internal memory or an external memory card. Alternatively, destroy all water sources, such as toilets and urinals in the entire game.

Jevons control mode:
Note: This code requires an analog controller. Pause game play and press Y(2), Z(2), X(2), Y, X, Z. The phrase "Jevons Control: On" will appear when game play is resumed to confirm correct code entry. The new controller functions are:

Analog-pad: View direction A: Action
X: Item
B: Move back
Z: Move forward
Y: Slide left
C: Slide right
L: Weapon
R: Jump
Up or Down: Item select
Left or Right: Weapon select