10 Constitution Points: In the code menu enter N_STINE to get 10 Constitution points
10 Dexterity Points: In the code menu enter ZXE053 to get 10 Dexterity points
10,000 XP Points: In the code menu enter DSP633 to get 10,000 Experience Points
500,000 Gold: In the code menu enter KNE637 to get 500,000 Gold 

Cheat List:
Press L+Y+A to access the cheat screen. Then enter one of the phrases to activate the corresponding cheat. For the cheats that give you items, hit accept multiple times to get more items: 

Credits: CREDITS 
Disable Cheats: UNBUFF 
Invincibility: PELOR 
Nightmare Difficulty: MPS LABS 
Unlimited MW: OBADHAI
Have 10 Antivenom Potions: SPINRAD 
Have 10 Will Potions (Medium): LU 
Have 10 Thrown Viper Axes: FRAZIER 
Have 10 Tomes of Lessons: PAQUIN 
Have 10 Thunderstones: ELSON 
Have 10 Fiery Oil: EHOFF 
Have 10 Flash Freeze: ESKO 
Have 10 Will Potions (Large): GEE 
Have 10 Insect Plague: DERISO 
Have 10 Tomes of the Teacher: MEFFORD 
Have 10 Thrown Halcyon Hammers: PRASAD 
Have 10 Thrown Axes of Ruin: ROMANO 
Have 10 Tomes of the Master: SPANBURG 
Have 10 Berserk Brew: THOMAS 
Have 10 Healing Potions (Large): THOMPSON 
Have 10 Globe Potions: WRIGHT 
Have 10 Rods of Destruction: AUSTIN 
Have 10 Fire Bombs: WEBER 
Have 10 Tomes of the Apprentice: BILGER 
Have 10 Rods of Miracles: JARMAN 
Have 10 Thrown Daggers of Stunning: BELL 
Have 10 Holy Water: CRAWLEY 
Have 10 Fire Flasks: BROPHY 
Have 10 Thrown Daggers: MOREL 
Have 10 Rods of Missiles: MILLER

This is just a exploit of the character join in, in the middle of game.

1. Player 1 finds an item he/she likes to duplicate.
2. Player 1 drops item.
3. Join in player 2.
4. Player 2 picks up item.
5. Save Game.
6. Player 2 drops item.
7. Player 2 leaves game.
8. Join in Player 2 from recently saved game.

(notice at this point Player 2 have 1 item in inventory and 1 item on the ground.)

Rinse and repeat steps 4-8

Note: doesn't work with soul shards (i tried).

Note: Remember that items have weight so let's say you have a 100 stack of 5 lbs Tome, the one who will use the items must be able to carry 500 lbs, if not you can not pick it up.

Note: If you pick up the item before you save then drop before you leave the items keep getting multiplied by 2.