Diablo

Duplicate items:
Place an item in your belt. Take the item to be duplicated drop it on the ground. Walk away without leaving the screen, then click on the item again. As you pick the item up, click on an item in your belt immediately before taking the item on the ground. If timed correctly, the name of the item that was duplicated will appear in the box down below. It will have the same appearance as the item on the belt that was clicked on. Drop the item on the ground or place it in the back pack and it will re-appear correctly. However, do not create a second item of the same type and put both on the ground. If this is done, the duplicate item will be destroyed.

Duplicate large items:
Put the item to be duplicated on the ground. Put a mana potion or another item on your belt. Walk a few steps away, then click on the item on the ground. Right when you pick it up, click on the item placed on your belt. Drop it on the ground. If timed correctly, it should turn into the item to be duplicated, and the original one will be in your inventory. This also works with money. Do not put both the duplicated item and the original item on the ground,or one will disappear. Note: This cheat will not work if the inventory window is open.
Information in this section was contributed by Logan Stromberg.

Keep more items:
In the town square by Cain the Elder, drop an item on the ground that you wish to keep out of your inventory but do not want to get rid of. Then, immediately save the game. The item will be in the town square until you pick it back up.
Information in this section was contributed by Bryan Vivian.

Defeating Zhar The Mad:
Walk towards a corner. He will follow and appear in front of you. Trap him in the corner. Hit him every time he appears, since he will be still trapped in the corner. If done correctly, you should not use any energy.

Defeating the Butcher:
First, meet up with him in his room. Then, lead him to one of the walls that look like cage walls. Go on the other side of the wall and close the door behind you. Shoot him with a bow or use magic. Since he cannot open doors, he will just stand there. Just keep shooting him until he is defeated.

Find the Butcher. Open his door and run away from him. He should follow you. Lead him to a staircase and run around it, but stay close to it. He should follow you in circles around the it. Eventually, after about thirty seconds to a minute, he should get stuck in the staircase. From there, shoot him with magic or a bow. You should also be able to melee attack him. Note: He can get away from it if you go onto the side of the staircase that you need to be on if you were to enter it.

Open the door, cast Fire Wall immediately, then close door after the spell. The Butcher will be stupid and stand in the flames provided you stay at the doorsteps. He will die almost always before the flame goes out, even if spell is cast by a Warrior. Note: You must be fast and need to proceed a few levels down in the dungeon to learn Fire Wall.

Note: You must be at the level 6 or greater with a strength of 30 or more for this trick. Buy one Fire Wall Scroll. You should be using a sword and a buckler. When you find the Butcher's room, stop in front of the door, open it, and go one step behind. When the Butcher shows up in the door, cast the Fire Wall in front of you, between you and the door. The Butcher will stop in front of you to hit you, and will start taking damage from the Fire Wall. After that, start attacking him. Even if you only hit him five or six times, he will die at the same time the Fire Wall disappears.

When facing the Butcher, get the best bow that you can use. Open the Butcher's door, lure him out, then run behind a cage wall. However, shut the door as he cannot open them. Then, take out the bow and shoot him repeatedly. Then take out a sword, bow, staff, etc. and attack him.
Information in this section was contributed by Steve Smith.

Buy Four Scrolls Of Firewall. Destroy all the monsters all around the Butcher's lair. Put all the Scroll Of Fire Walls on your belt. Go directly in front of the door and use a scroll. Go back one and use another scroll. Go back and use another scroll. Go back one more time and use the last scroll. If done correctly, the Butcher should be dead.
Information in this section was contributed by Lego7C.

Defeating Diablo:
Lure out the lesser monsters a few at a time and kill them. This reduces the number of enemies that come after you. When Diablo comes after you, get your back against a wall. He will not be able to knock you back and you can keep hitting him.

Go to the witch and get Firewall, Flamewave, Fireball, Mana Shield and Stone Curse. Duplicate the items as many times as possible. Read all of the books. If playing as the Wizard you can read more books. Buy as much Mana as you can get in the inventory and the hotkeys. Return to Diablo's level and activate Mana Shield. Kill off the smaller monsters with Fireball. When you get to the main part where Diablo is located, cast Firewall as many times as possible. Refill on Mana, then cast Flame Wave as many times as possible. Refill Mana again. When Diablo gets into view, run in to one of the smaller rooms on the side. When he enters after you, Phase or Teleport out and set Firewall in the room. When he exits the room, remain about a hands length from the door and you should be able to kill him with fourteen to nineteen Fireball spells. When he is chasing you, fill the hotkeys with Mana and you should be fine. If you want to stay away from his spell, just keep moving.

As a sorcerer, get to about level 25, and make sure you have a high level Holy Bolt (10 or higher). Finally, make sure you have plenty of Mana. Go to where Diablo is located, kill the enemies around him, then blast him with Holy Bolt. Since Holy Bolt is at such a high level, it will shoot very quickly and Diablo will not be able to move or get out of the way.

To avoid having to kill all of Diablo's minions first, use your automap (press [Tab]) and line your character and the small orange arrow up so that they are exactly together. Then, stand in the opening of the third room of levers that is facing Diablo's chamber. Line yourself up with the opening, using the map, to his room without leaving that doorway. This works best with a Rogue and a very strong bow, but any sort of projectile spell will also work. Shoot directly ahead until he smacks you with his fire spell. Then, teleport frequently unless your character is very strong. Alternately, you can get your back against the wall so that he cannot knock your back.
Information in this section was contributed by ~MegaKat~.

Defeating King Leoric:
Run in circles so that he cannot hit you, and have another player attack him in the back.
Information in this section was contributed by andre tocco.

Get your character to about level 10. Enter his tomb and take out all the minions that you see. There will be several rooms all with minions in them. Before every room, go to the very edge of it so you are not in the room, but can see inside. If you see an archer to the left and another to the right in a very big room, save the game, Charge in and make sure you have the Fire Wall spell and at least two Full Mana potions. Cast Fire Wall as many times as you can in the middle of the flood of monsters that attack you. Make sure you do not allow any skeleton minions to get behind you (archers do not matter). Eventually, you will see an extremely big skeleton come after you. This is King Leoric. Wait until he is within striking distance of you, then run away as fast as you can. Make sure he is directly behind you. Lead him to the room that you would need to be in to exit his tomb. If there are any enemies here besides him, lead them all back into the big room and kill them. If Leoric is left alone in the same room as any of his dead minions, he will resurrect them. After Leoric is led into the room that you would need to be in if you were to exit the tomb, do so if necessary and cast a Town Portal. Buy five more Town Portals and completely heal and fill your belt with health potions. Return to Leoric's tomb, but do not enter it. Get directly outside of it and save the game. Then, enter it and he will be waiting for you. Hack away at him until he has almost killed you. Once again, climb up the stairs and refill on health and mana. If needed, go back to town and buy more items. Leoric will not refill on health, allowing you to repeat this until he is defeated.
Information in this section was contributed by RON PENCE.

Hint: Defeating hordes of monsters:
If you are facing a horde of monsters that you do not want to crowd around you, get on the side of a doorway opposite the monsters and stand directly in front of it. By doing this, only one enemy at a time can attack you and you do not have to worry about being overrun.
Information in this section was contributed by ArisuReaper.

Hidden commentary:
Click on a cow multiple times and the game will say "Yep, that's a cow all right." Keep clicking and it will say "I'm not thirsty." Click some more and it will say "I'm no milk maid".
Information in this section was contributed by roy 3003.