Question: what name do you give eevee to evolve into leafeon?
Answer: Simply edit the name of your Eevee prior to evolution, and you can guarantee the specific Eevee-lution you'll receive. Note that the trick only works once for each Eevee-lution, so if you're looking to get two or more Leafeon or Gaceon, you'll need to get your hands on some additional items.