Pokemon Gold/Silver Cheats

After you get evee from bill and you want the evil evee then when its
night go to the underground tunnel and go to the guy that makes people
happier. Than tell him you want Evee happier. Only do that once a night. 
Than do that 3 nights. then fight with him. He should evolve when he
raises a level. Than to get the good evee do the same thing but during
daylight. If you do the bad one he will not act evil to you.

Every Wednesday, your rival shows up at the stairs leading into the pokemon league, eager for revenge! Its easy experience, and his pokemon never grow levels!!!

To unlock this item, you must have fly to get to Azalea town for Kurt

AVOID RANDOM BATTLES

When you walk up to the edge of grass use cut and the grass will be gone. No more random battles.

EASY BREEDING

If you capture a Ditto you can use that for breeding. The Ditto will act as the female, so you wont have to get two of each type of Pokemon that you want the baby form of it. For Example just breed a Ditto and a Pikachu, and you will get a Pichu.

BATTLE LEADERS OVER AND OVER AGAIN

First you save in front of a PC and then you go and battle the Gym and its leader. When you finish, go and clone the pokemon that grew levels. When you turn your game back on you will be in the Pokemon center BEFORE you battled the leader but if you look in your PC you will find the Cloned Pokemon. Exchange the pokemon and save when you have your raised ones in your party then you can do it again.
Note: This trick will fill up your boxes so every three times you do this trick release the extra pokemon or switch boxes.

DUPLICATE

NOTE: This requires at least two pokemon, and access to a PC.
First, take the pokemon you want to duplicate, put it into your group. Make sure you have a box with at least one free slot. Save your game in front of your PC. Then, go to the box, and deposit the pokemon. Exit the box, go to ''Change Box,'' select any box, and while it's saving, turn off the Gameboy.

NOTE: Make sure that you do it while the message ''Saving, do not turn off the power'' is still there. Otherwise it will not work.

Turn on the Gameboy, the box should be the one that you deposited the pokemon in. You should have the pokemon in your group and have the same pokemon in your group.

(also works in crystal version)
Have u wondered how to multiply pokemon or rare items??heres whatcha do:
give a pokemon(such as ho-oh, lugia,ect)an item (such as a rare candy,masterball,ect), and save the game next to a pokemon pc.deposit that pokemon. then switch the box.whenever you save, an icon says:"saving.... dont turn off the power".but before the sentence ends,(when it says "power",its to late)cut off the game(no, it does not hurt the game nor gameboy, or delete any items you may have).turn it back on,withdraw the pokemon in the box, and you should have 2 of the pokemon and of the item!cool huh?