I have been playing a Priest deck lately for ranked play and it works really well. It wrecks Zoo... I don't think I have actually lost a game to zoo with it in fact. It is weak against control warrior, but otherwise pretty strong against everything else (although getting the deathlord hunter's marked by a Hunter sucks lol).

Here is the deck I am currently using:

Circle Priest


Ways to clear opponent's board:
Soulpriest+Circle of Healing = 4 damage to all minions (soulpriest lives)
Wild Pyro+Holy Nova = 2 damage to enemy minons, then 1 damage to all minions (3 total to enemy minions)
Holy Nova
Wild Pyro+PW:Shield+any other spell = 2 damage to all minions

Other Combos:
Blademaster+Circle of Healing = 4/7 minion on turn 3
Northshire Cleric+any healing = insane card draw

This is a tricky deck to play though. You need to avoid mistakes with using wild pyro and soulpriest, because they are cards that can easily lead to mistakes. For example, don't cast holy nova or holy fire with a soulpriest out, since it will damage your minions or you. Also, don't forget you have your soulpriest out and try to heal yourself or one of your minions with hero power. With wild pyro out, don't cast a spell when you have a 1 health minion... heal it or trade it first. I have made many mistakes with these two cards in the past, but once you stop making them and know how to use them in this deck, they are awesome.