Glitch 1 - Bad EGG
If you cheat to get a Pokemon, a Bad EGG will appear. It only effects the first Pokemon in the party if in the party. If it is in the PC, it will turn everything into a Bad EGG or Golden Bulbasaur. After it spreads, all the Pokemon will be gone and you might have to restart your file.
Glitch 2 - ??????????
Ten Question Marks/Decamarks is a glitch Pokemon which is encountered in the wild with a sprite of an "undiscovered Pokemon" from the Pokedex. This is usually found when you cheat to go into battle without a Pokemon. In Ruby/Sapphire, this glitch can occur if you find a Pokemon that is not in the Hoenn Pokedex before the get the National Pokedex.
Glitch 3 - Nurse Joy is CRAZY!
Go into a Pokemon Center with no Pokemon, ask Nurse Joy to heal your Pokemon, and she will place a million Pokeballs all over the game and you can't move your character because Nurse Joy is still healing.
Glitch 4 - Become other people/Clone yourself
This has only worked for me. Go walking by an NPC, and when he/she is 1 tile diagonal from you, quickly press START, go to Pokedex, and close it to find yourself cloned, yourself as the opposite gender player, or as the NPC that was just walking by.
Glitch 5 - Pomeg Berry
Get a Pokemon down to one HP and make sure only a 1 or 2 HP Pokemon is in the party with an egg. No other Pokemon. Use a Pomeg Berry on the low HP Pokemon and you can now see what is inside the egg, along with moves, ability, nature, etc. and you can use the egg in battle now!
Glitch 6 - Dive Glitch
While entering an underwater cave, if the player presses the B button at the right time, the game will ask the player if he/she wants to resurface while on top of the entrance.
Glitch 7 - I'm walkin' on sunshi- er... water!
Resurfacing from the entrance to Seafloor Cavern or the Route 104 entrance to Marine Cave will cause the player to resurface on a rock tile instead of a water tile. The player can then walk on the water, but cannot go back on land this way. While walking on water, wild Pokémon can appear. It is not possible to mount waterfalls or fish. Using Dive then resurfacing normally, or Flying or Teleporting to any location will fix the glitch.
Glitch 8 - Off the Wall!
By using this glitch to land on a door tile, then cancelling instead of surfacing, it is possible to save on a door tile. If the game is saved and reset from a door tile, the player will be sent forward one tile in the direction they were facing upon saving the game. Saving on a wall tile does not yield any similar effects.
Glitch 9 - You're out of boundaries!
By performing this glitch on the entrance to Marine Cave on Route 129, it is possible to access an area normally behind rocks. An invisible wall prevents players from leaving the map.