If you want something that actually works it's pretty much a choice of Vaporeon, Umbreon or - possibly - Jolteon. Most eeveelutions fail miserably, either by movepool or statline (or, in some cases, both). Glaceon has great SAtk and SDef, but its crappy HP and Speed combined with its dismal special movepool make both these strengths moot and Leafeon suffers from much the same problem except that it's on the physical side, and Flareon is the saddest thing gameplay-wise since Delibird and Unown. EDITNESS: Fine, since a certain smarty-pants moveset mod pointed it out to me: Espeon has gone up to useful with the addition of special Shadow Ball and Grass Knot to its movepool. Usually, there are far more interesting and effective pokémon choices than eeveelutions, though.