This game is similar to The Never Ending Cheat .
But, you post a whole cheat but don't make it too long or it will never end anyway. It must work in one, two or all generations, including XD and Colosseum. Formally to start!
How to get Jirachi in your game without Ticket, etc. (Ruby, Sapphire, Emerald)
Start a new game. Pick to play as female and when Birch says " This is a Pokemon...." blah-blah press this in this sequence: A, B, A, Start, Select, L, R, L, R, The brighten-the-screen button and turn the volume to its loudest.
Let the beginning of all sequence finish and instead of in a truck, you will be in a rocket and it will go beep-beep-beep and explode. If you don't die, good. But you only have a 10% chance to survive. Because if you die, Giratinas will devour you! If you don't die, you will be in your room. Go to the PC, and there will be 20 Master Balls. Withdraw 1. walk: 6 steps left, 5 steps down, 4 steps right and 3 steps up. The Master ball is gone, but you have now a Jirachi. Go into the grass up Littleroot, the kid will admire you and say... You're my hero! Don't save the not-bright Professor running like crazy there. Don't mind, Professor. He'll run out of stamina and the Zigzagoon/Poochyena will eat him after that. Now you have a Jirachi as a starter. And fight your rival, which will have a level 1 Zigzagoon.
Game from Lugia's Island Forums