Diablo II

Cacophony of Sound
During gameplay, press Enter, then type: SOUNDCHAOSDEBUG to hear an uproar of voices and sounds. To turn it off, type it again.
(Thanks to andrew_cotes@hotmail.com)

Keep Items after Death
Press ESC, then Save and Exit the game if you are about to die or have died to find yourself in the safety of the town upon rebooting.
(Thanks to andrew_cotes@hotmail.com)

Necromancers Weapon
To attain the Necromancers ultimate weapon, the STROKE OF DEATH, please do the following:
Summon one of each of the golems
Cast a bone spirit
Then die.
After you respawn, type in the phrase: THE DARK MUST FEED
Look in your inventory and you will have the Stroke of Death.
(Thanks to Poach_256@HotMail.com)

Paladins Weapon
To attain the Paladins ultimate weapon, the Holy Avenger, please do the following:
Cast the following spells in this order: Meditation, Prayer, Concentration, Prayer, Prayer, Meditation, Concentration, Meditation.
Then kill a monster using the spell, HANDOFGOD
Type: I HAVE SERVED YOU
Look in your inventory and you will have the Holy Avenger.
(Thanks to Poach_256@HotMail.com)

Secret Cow Level
After beating the game on all the modes (Normal, Hard, Hell), combine Wirts leg with a tome of Identify that is full in the Horodric Cube and it will be empty. Then a portal will appear next to you. You have to be in the Rouge Encampment.
(Thanks to Poach_256@HotMail.com)