There are many codes in the game of Pokemon that do not require the Gameshark. I will list the codes in order of importance to me, from top to bottom.

HOW TO INCREASE THE QUANTITY OF YOUR ITEMS

To get more than 100 of an item, perform the following steps:

1. Fly to Viridian City and talk to the old man who says that he wants a coffee.
2. When he asks you if you are in a hurry, say no and allow him to teach you how to catch a Weedle with his pokeball.
3. Immediately fly to Cinnabar Island, have your special item as the sixth item in your item box (press Select to switch items around), and surf on the right coast. You will fight some high leveled pokemon.
4. When you fight Missingno, whose picture appears to be screwed up, run away from battle.
5. Check your item box now. The sixth item should have a number and a little flower beside it.

Remember, you need to have that item with you first.

HOW TO CATCH HIGH LEVELED POKEMON!

To fight wild pokemon that appeared the last place you went to and are over level 100, perform the following steps:

1. Walk around in the patch of grass with the pokemon you want.
2. Fly to Cinnabar Island and surf on the right coast.
3. You will fight the wild pokemon that are found in that patch of grass; the pokemon will be around level 132. If you make them faint, you will gain around 3000 experience points.

The best place to use this cheat for is the Safari Zone.

MORE COINS

There are several ways to get more coins for the Celadon Game Corner. Perform each way below:

1. Talk to the people in the Game Corner; you can get 50 coins in total from all of them.
2. Win coins from the slot machines, this is very hard.
3. In the secret hideout of Team Rocket in Celadon City, walk around and keep on pressing A. You will find lots of coins this way.
4. Talk to the man in the top left corner of the Game Corner. For every 1000 dollars you give him, he will give you 50 coins.

If you really want the pokemon prizes next door to the Game Corner, do the Item Multiplying Cheat for Nuggets or Rare Candies. You can sell nuggets for 5000 dollars each

BETTER CHANCHES OF CATCHING POKEMON

To have a Pokeball, Great, or Ultra Ball function as a Masterball, perform the following steps:

1. When you throw the balll, press and hold Up and B while the ball closes in on the wild pokemon.

You will need exact timing to do this.

To get the Pokeball to close in tighter on the wild pokemon, perform this step:

1. Keep on pressing A when the pokeball is closing in on the pokemon.

SECRET POKECENTER

This is kind of useless. This is kind of funny, though.

1. Go to the people hotel in Celadon City and treat it like a Pokecenter.
2. Go to the blank space on the very right and press A. You can access the computer from there.