You'll be surprised how much this one works.
Blissey (F)@Focus Sash or Focus Band
Ability: Natural Cure
Nature: Gentle (-Def +Sp.Def) or Calm (-Atk +Sp.Def)
EVs: 252 HP 252 Sp.Def 4 Speed
-Counter: Here's where you use that item. Because of extremely low Defence and extremely high HP, if the opponent walks into Counter they will not live to tell the tale.
-Toxic: You can see where I'm going here.
-Protect: You guessed it.
- Soft-Boiled: Works well if you rotate between this and Protect when facing Special Attackers after Toxic. Counter is for Physical opponents.
This one is prepared for pretty much anything, barring Steel- or Poison-types with special moves, physical Ghosts, or anything that runs Rest+Sleep Talk with special moves. Other than complications like that, you're golden. :)