Vaporeon

Vaporeon's cell composition is much alike to water molecules.  This makes Vaporeon capable of melting away and becoming invisible in water.  It's long tail that's ridged with a fin is sometimes mistaken as a mermaid.  When its fins vibrate, it means some rain will come down in a few hours.
Vaporeon is probably one of the most favored of all the Eeveelutions.  Eeveelutions are what people call evolved forms of Eevee.  It is one of the original Eeveelutions that has really good stats.  It has low Attack, Defense, and Speed, but on the other side, it does have good HP, Sp. Attack, and Sp. Defense stats.  Vaporeon has several good Special Attacks.
It has numerous Water-Type moves.  You might want to give it Scald, because it might Burn your opponent.  That's just awesome.  It can also learn Hydro Pump, and some Ice-Type moves, such as Ice Beam or Aurora Beam.  If you keep it as an Eevee until Level 36, can learn Baton Pass.  If Vaporeon has any stat changes, like having its Attack stat go up by 1, for example, the Pokemon replacing Vaporeon would have its Attack stat go up by 1 as well.  You could give Vaporeon Acid Armor, use it, then use Baton Pass, making the Pokemon that's taking Vaporeon's place will have its Defense stat sharply raised.  Thats the power of Baton Pass.
Vaporeon's ability is called Water Absorb.  If you are hit by a Water-Type move, you have some HP restored.  But most people are smart enough to know that if you try to attack a Water-Type with a Water-Type Attack, it'll just be Not-Very Effective anyway.  But still, Water Absorb can be useful.
Vaporeon is a really good Eeveelution and it'll probably continue to be good as Pokemon moves on.