W-Item Duplication Bug
From Final Fantasy Wiki
The W-Item Duplicated Bug is a very useful glitch in the game Final Fantasy VII. The W-Item Materia is a Command Materia that allows a character to use two Items at once. To make the glitch work, enter a battle and select any item you wish to duplicate. Confirm that you want to use it, then select another item, it does not matter which one. Then when the arrow is over a character's head, cancel the item with 
(it does not work with 
). Every time you do this, the amount of your first item will go up one. The glitch cannot exceed the 99 item cap.
Because you can make 99 of any item in battle, this glitch is obviously extremely useful. A player can boost his inventory to have 99 Elixirs and Megalixirs in a matter of minutes. It is also the only way to get 99 Dragon Fangs.
There is also a potential draw back to the glitch. If the first item is selected, it is removed from the inventory even if the item command is canceled and the item is not used.
There is another, more potent version of this glitch, which allows a player to get 99 of anything in the game, though it requires more work and effort than with the original glitch. In order to pull this version off, say you want 99 Power Sources. Get rid of all Power Sources in your current inventory, then have at the very top of the list just 1 of an item you can use in battle (like say, 1 Potion). Have one character with a long attack or steal animation with Morph/Steal, and another character with the W-Item materia. Enter a battle with an enemy that has a Power Source that you can steal or morph (in this case, Morph). Next, have your Morpher/Stealer attempt to Morph/Steal the item, and while they're doing that (hopefully the animation is long enough), have your character with the W-Item materia use the very top item in the list. If all goes well, and if you steal/morph successfully, the item that you just got will be at the top slot and you can perform the normal W-Item trick to get 99 of that item. The following are the only things to not work with this glitch :
- Battery
- All Limit Manuals
- Save Crystal
- Guide Book
- Buster Sword
- Gatling Gun
- Silver Barette
- Seraph Comb
It is also possible to get 198 of anything if done right. Just perform the above tactics and you will end up with a second stock of the same item. For the non-stealable/morphable items, or for the rare items like Mystile, to get 99 of these, you will need to have an enemy Steal it from you, then kill the enemy quickly before it runs off and while that character is attacking, perform the above steps.
