Best in slot at level 20
The beta caps characters at level 20. Each list ranks the gear a character can reach by then, slot by slot, for Alliance and Horde, with the talents it was built around and the character stats it adds up to.
Warrior
Warrior PvPArms 6/5/0, 
Smite's Mighty Hammer
Warrior PvEFury 0/11/0, Smite's Mighty Hammer
Warrior TankProtection 0/0/11, 
Butcher's Slicer
Paladin
Paladin RetributionRetribution 0/0/11, 
Verigan's Fist
Paladin HolyHoly 11/0/0, 
Taskmaster Axe
Hunter
Hunter PvPDamage 0/0/11, 
Impaling Harpoon
Hunter PvEMarksmanship 0/11/0, Impaling Harpoon
Rogue
Cruel Barb
Priest
Priest ShadowShadow 0/0/11, 
Witching Stave
Priest HolyHoly 0/11/0, 
Staff of Westfall
Shaman
Shaman ElementalElemental 11/0/0, 
Staff of the Blessed Seer
Shaman EnhancementEnhancement 0/11/0, Smite's Mighty Hammer
Shaman RestorationRestoration 0/0/11, Staff of Westfall
Mage
Evocator's Blade
Warlock
Warlock PvPAffliction 11/0/0, 
Staff of Soran'ruk- Warlock PvEAffliction 11/0/0, Staff of Soran'ruk
Druid
Druid FeralFeral 0/11/0, Smite's Mighty Hammer
Druid BalanceBalance 11/0/0, Staff of the Blessed Seer
Druid RestorationRestoration 0/0/11, Staff of Westfall