Level select
Pause the game and quickly press Up, Down, Left, Right, Left(2), Right(2). If you entered the code correctly, Spawn will speak.

All weapons
Pause the game and quickly press Up, Down, Left, Right, Left, Right, Left(2). If you entered the code correctly, Spawn will speak.

Infinite ammunition
Pause the game and quickly press Up, Down, Left, Right, Up, Left, Down, Right. If you entered the code correctly, Spawn will speak.

Infinite Necroplasm
Pause the game and quickly press Up, Down, Left, Right, Down, Left, Up, Right. If you entered the code correctly, Spawn will speak.

No blood
Pause the game and quickly press Up, Down, Left, Right, Up(4). If you entered the code correctly, Spawn will speak.

Unlock all comics
Pause the game and quickly press Up, Down, Left, Right, Right, Left(2), Up. If you entered the code correctly, Spawn will speak.

Unlock encyclopedia
Pause the game and quickly press Up, Down, Left, Right, Left, Right, Up, Down. If you entered the code correctly, Spawn will speak.