Anyone who visits Gamestop before October 26 with either a copy of Pokemon X or Pokemon Y in tow will be given a totally gratis Shiny Gengar. What's more, the rare Pokemon - Bulbapedia claims Shiny Pokemon have a 1 in 4,096 chance of appearing in the wild - will be holding a Gengarite Mega Stone, allowing the ghostly 'mon to Mega Evolve into an even more powerful pocket monster.
Best of all, there's no catch. You don't have to buy anything, sign up for a rewards card or even glance at the pre-owned games wall. Simply walk into your local Gamestop, politely ask an employee about the promotion and they should walk you through the process of downloading the Shiny Gengar.
[Image: Nintendo/The Pokemon Company]