Umbreon @ Leftovers Synchronize 252HP/4Def/252SpD Calm Nature -Foul Play -Wish -Protect -Heal Bell
Standard? Absolutely. But it fills the roles of Wish Passer, Special Wall, Cleric, Status Absorber, Status Passer (sync). It is so valuable, it is the first member of the team every time. Plus it's like my second favorite poke of all time anyway, and if it had come along in first gen, Wartortle maybe wouldn't have been number 1.
I bred a perfect (ish) one of these in Gen 5 just so i could have a legit one to use in gen 6 with HB and FP.
3DS FC: 1134-8061-2200; SV 3273; IGN: Dano; List: http://tinyurl.com/meg2s5l Beartic, Piloswine, and Snorunt - My Friend Safari is Ice because I'm so cool.
You'd be surprised how much of a tank she becomes. Shadow Ball for STAB, the Dazzling Gleam of her adorable necklace covers Dark types. Will-o-wisp gives her residual damage and let's her take physical attacks better, Pain Split for recovery, because that's her thing.