Easy Money
When you are in the Gold Saucer Prison, go into the desert and walk around. You will eventually fight a little cactus man. You only can kill him with the Choco/Mog summon materia, when you kill him he gives you 10,000 gil!
Getting Yuffie
When you are in a forest, walk around. You will encounter a strange girl. When you defeat her, you will be in a grassy area. DO NOT USE THE SAVE POINT! She will run away a steal some money. When she asks you questions answer like this:
1)When she asks for a rematch, respond "Not interested"
2)When she asks if you are afraid, respond "petrefied"
3)When she is about to leave, respond "Wait a second"
4)When she asks to join you, respond "That's right"
5)When she wants to tell you her name, respond "Let's hurry on"
Getting Vincent
When you are in the Shinra Mansion in Nibelheim, go to the second floor, to the left and to the top room. You will see a safe. The combo is:
1)Right to 36
2)Left to 10
3)Right to 59
4)Right to 97
Make sure you answer it quickly and don't go over the number or it won't work. When you open it you will fight a boss. When he is defeated, you will get Cosmo Memory, Red VII's ultimate limit break, the Odin materia and the basement key. Go to the basement and go through the purple door on the second screen of the basement. There will be a puple coffin. Vincent is in it. Talk to him until he doesn't want to talk anymore. When you leave, Vincent will ask to join you.
Tropical Getaway
In Costa Del Sol, there is a man trying to sell a condo. The price is 300,000 gil. You can go there anytime and rest for free. This is nothing but a waste of money. You can use the Inn there 1,500 times for the price of the condo.
Secret Cinema
After Cloud finds himself in Mideel, Go to the Shinra Mansion in Nibelheim. When you enter the library, you'll see a special cinema, which explains how Cloud became a mercenery.
Lucky 7's
When a character's hp are reduced to 7777, they will get "All Lucky 7's!". They will do 7777 points of damage until there hp isn't 7777. When the battle is over, that character's hp will be 1, so watch out.
Get to the Ancient Forest before Disc 3
To get to the Ancient forest easy, breed chocobos 'till you get a black one. Then you can get to the Ancient Forest.
Getting the Cursed Ring
When you are Cid, go to Mideel and go to the house where the Accessories Shop is. Go behind the man outside of the house and walk a little bit behind him. You will hear a chime. Press the circle button. Cid will find a Beat-Up Key. Go to the Weapons shop. Try to open the door with the key. You can't. When the weapon seller asks what you are doing, answer him truthfully.
Password for Huge Materia
The password for the lock in the rocket is "circle, square, x, x".
Key to Midgar
After you have gone through Midgar your second time, go to Bone Village. Tell the digger you want to look for a "normal treasure". Then go up the ladder, to the tent-like thing's opening. Place a bunch of diggers there. Ignite the bomb and go to where all of them are looking at. There you should find "The Key to Sector 5".
Note: Visit the weird item shop in the beginning of Wall Market. Try the broken Machine, you will get Tifa's Ultimate weapon. Visit the weapons shop too, the man that makes stuff will sell you the "Sneak Glove" for 129,000 gil. It will help you steal. Finally visit the church on your way out, you will see Aeris's ghost.
The Backroom
After you have gone through Midgar for your second time, go to Cosmo Canyon. Go to the General Store with the old lady. You can now go to the backroom, through the place where it was roped off. There you get an Elixer, Magic Source and the "Full Cure" materia.
Oxyn Weapon
I don't know if this code works or not, but to fight the Oxyn Weapon you need to breed two Gold Chocobos together. The chocobos both have to have 999 stamina and speed over 150. It is very hard. I have never done it.