Hexen 64

Enable cheat menu:
Pause the game play and hit C-Up, C-Down, C-Left, C-Right. You will see
the cheat menu at the bottom of the menu. Go to the cheat menu and quickly
enter the following button combinations. Note: If the code is accepted,
you should hear a sound.

Destroy all visible enemies: Press C-Down, C-Up, C-Left(2 times).
Get all artifacts: Press C-Up, C-Right, C-Down, C-Up.
Get all keys: Press C-Down, C-Up, C-Left, C-Right.
Get all puzzle items: Press C-Up, C-Left(3 times), C-Right, C-Down(2 times).
God mode: Press C-Left, C-Right, C-Down.
Maximum health: Press C-Left, C-Up, C-Down(2 times).
No clip mode: Press C-Up(20 times), C-Down.
Stage select: Press C-Left(2 times), C-Right(2 times),C-Down, C-Top.
Unlock all weapons: Press C-Right, C-Up, C-Down(2 times).