Hats off to Sk8rGuy for the following cheat. A semi-automatic controller and a couple of strong rubber bands are required for this to work. When your characters have reached level 60 in the game, visit the Midgar Zolom and save your game in
the swamp. Once you've accomplished this, turn the semi-auto switch/button on and put the rubber band over the (O) button. By leaving your game on overnight, you should find levelling up your characters very easy.
Lotsa GP (PlayStation)
Ever wanted to gain lotsa GP with minimal effort? If you have a turbo controller, follow this cheat by J. White. With your turbo controller, have it pushing to the upper-left corner and a weight placed on the O button. Go to Wonder Square and use the Arm-wrestling machine. Activate the turbo button on O and situate the controller to pull to the upper-left corner. Leave it overnight, and by morning you should have plenty of GP without breaking a sweat. Note that you may need a large sum of Gil to pay for the arm-wrestling machine.
Item Duplication (PlayStation / PC)
This cheat allows you to duplicate (almost) any item. You must have at least two items for this to work. Equip the W-Item materia and enter battle. Select the W-Item command and use the item you want to duplicate. Then choose the second item. However, do not actually use the second item on a monster. Select it so only the cursor appears on the monster. Then cancel. You will find the quantity of the item will increase by one. Repeat as you desire.
Chocobo Races (PlayStation / PC)
In the PlayStation version, hold down L1+R1 when racing your chocobo to boost stamina. Contributor Dark Half notes that in the PC port of FFVII, using End and PgDn has the same effect as L1 + R1 in the Playstation version.