Below are the cheat codes for Hexen II. To use them you can either go to the console by pushing the escape key during gameplay, or, as I recommend, just press the ~ key and the console will pop up. (It's really fun to turn yourself into an invincible sheep, them fly around your enemy's head nibbling his ears! "Iron" Bo Peep!)
Cheats
CHANGELEVELx: warps you to level x (insert a number).
CHASE_ACTIVE 1: chase camera mode (third person viewpoint).
GIVE H 999: grants 999 health (or value you substitute).
GIVE 2: grants weapon 2.
GIVE 3: grants weapon 3.
GIVE 4: grants weapon 4.
GOD: toggles god mode.
IMPULSE 9: grants all weapons and full mana.
IMPULSE 10: changes your weapon.
IMPULSE 13: lifts an object.
IMPULSE 14: temporarily turns you into a sheep.
IMPULSE 22: toggles permanent crouch mode.
IMPULSE 23: grants a torch.
IMPULSE 25: grants the tome of power.
IMPULSE 39: toggles flying mode.
IMPULSE 40: increases your experience level.
IMPULSE 43: grants all weapons, full mana and all items.
IMPULSE 44: throw an item.
IMPULSE 99: restart the level.
IMPULSE 100: uses the torch.
IMPULSE 101: uses the quartz flask.
IMPULSE 102: uses the mystic urn.
IMPULSE 103: uses the krater of might.
IMPULSE 104: uses the chaos device.
IMPULSE 105: uses the tome of power.
IMPULSE 106: uses the stone of summoning.
IMPULSE 107: uses the invisibility sphere.
IMPULSE 108: uses the glyph of the ancients.
IMPULSE 109: uses the boots of speed.
IMPULSE 110: uses the repulsion disk.
IMPULSE 111: uses the seal of the ovinomancer.
IMPULSE 112: uses the ring of flight.
IMPULSE 113: uses the force cube.
IMPULSE 114: uses the icon of the defender.
NAME x: changes your name to x (substitute name).
NOCLIP: toggles clipping mode.
NOTARGET: toggles enemies' ability to sense your presence.
RESTART: restarts the level