“Final Fantasy VII” is not perfect, it has several bugs and one of which can be exploited for large amounts of rare items or an easy way to obtain tons of Gil fast. The way to do this is known as the unlimited item glitch.
In order to do this, the player must first acquire the W Item Materia, which is located on the Midgar Train Tracks towards the end of disk 2. Afterwards, simply equip said Materia to any character in the active battle party. After this, one must get into a battle, preferably against an easy enemy so that the player doesn't actually have to try to stay alive and can simply focus on accomplishing the glitch.
Once the character equipped with the specific Materia is up to bat, select the W Item command from the list, and select any item other than the one that is wished to duplicate. When prompted to select a second item, then it is time to pick the one that is desired to obtain many of. In “Final Fantasy VII” when selecting an item, after the player selects it initially, he or she must then choose a target for said item in battle. Once the second item is initially selected, the trick is to not select someone to use it on, but rather to cancel the selection all together.
After doing so, the number of the selected item should increase by 1. This can be done repeatedly to obtain 99 of every item, which one can then decide to sell for massive amounts of Gil or keep and, for example, have unlimited Megalixirs or 99 of a Source item for stat boosts. In conclusion, the glitch is useful for those who wish to simply have reward without working for it, or if someone simply wishes to obtain multiple of a rare item that, once used, can not be obtained again in that play-through.