Who wouldn't like a free shiny Pokémon!? Now, players can add another shiny Pokémon to their roster. Players can do so by going to GameStop. They are currently giving away two special Pokemon to help promote some upcoming releases.
If you go to GameStop between October 13 and October 26, you can get a card containing a code for a Shiny Gengar for Pokémon X/Y. This Gengar will also come holding a Gengarite Mega Stone to allow it to Mega Evolve into a Shiny Mega Gengar.
After that, from October 27 to November 16, GameStop will be offering Diancie in Pokémon X/Y. Diancie will be able to be transfered from X/Y to Omega Ruby or Alpha Sapphire. After the transfer, you will be able to get a Diancite Mega Stone to Mega Evolve into Mega Diancie.