Umbreon

When Umbreon is exposed to the moon's aura, the rings on its body faintly start glowing, giving Umbreon a peculiar power.  It will also fear in the hearts of anyone who passes by Umbreon.  It evolved when it was exposed to the moon's waves and energy pulses.  It hides to in the bushes and waits for prey to pass by.
Umbreon is the Dark-Type Eeveelution.  Umbreon has a normal amount of HP in stats.  It has high Defense and even higher Sp. Defense stats.  Unfortunately, Umbreon has low Attack, Sp. Attack, and Speed stats.  The fact that Umbreon is slow doesn't exactly make it the easiest Pokemon to work with, but at least you have high Defensive stats.  The low Attack and Sp. Attack stats makes it hard for Umbreon to hit any opponents.  It's usually better at taking hits than sending them.
For all the people who see the computer players in the Pokemon games using Umbreon,you know they're always gonna use Payback or Pursuit.  How does it work on actual controlled Umbreon?  Although it is low, Umbreon has higher Attack stats than it does with Sp. Attack stats.  Payback is Physical, and gets twice as powerful when Umbreon takes damage the same turn from the opponent.  Since Umbreon is slow, it works perfectly with Umbreon.  Giving Umbreon moves capable of becoming twice as powerful as they already are or moves with high base powers is the best way to go.  Try equipping Umbreon with Giga Impact or Retaliate. You might want to give it strategic moves as well, like Toxic or Attract or even by breeding, Wish.  Just keep in mind to not use Umbreon as a staller.
Like Espeon, Umbreon's ability is Synchronize.  If you are Burned, Poisoned, or Paralyzed, the status condition is passed on to the foe.  It's a great ability, and works better in some battles than in others.
So Umbreon isn't exactly the best Eeveelution, just in the middle.  If used very carefully, Umbreon might be a good Pokemon for you.