Our favorite item for EV training isn't actually an item, but a virus. The Pokerus virus might sound like a horrible illness, but it's something you actually want your Pokemon to have. A Pokemon infected with Pokerus will earn double EV points for the rest of its life. There's a rare chance your Pokemon will get Pokerus in a random battle. That said, it's much easier to make some friends (try our Pokemon forums!) and have them trade you an infected Pokemon.
One thing to keep in mind is that Pokemon can only spread the virus for a limited time. So if you're lucky enough to have a Pokreus-infected Pokemon, go ahead and infect several more by having them in your party and battling. Put some of the infected Pokemon in your PC (where its contagion time will not decrease) to spread Pokerus to other Pokemon at a later date.
