Jolteon, Vaporeon, Flareon
If you remember the Pokémon Season 1 Episode 40 "The Battling Eevee Brother's", Ash gets to meet the trainers of Jolteon, Vaporeon and Flareon. The trainers of these three Pokémon's were Sparky, Rainer and Pyro. In order to evolve your Eevee into any of these three, then you have to rename your Eevee to the respective trainer's name, i.e, Sparky, Rainer and Pyro to evolve to Jolteon, Vaporeon and Flareon respectively. Here is a link showing the evolution of Eevee into Vaporeon: https://www.youtube.com/watch?v=Ky-WW8tUIQQ. If you have any questions, please post them on my wall, I will guide you with my experience. I hope you find them useful.