Hearthpwn

The power of this deck lies in an incredible synergy between its cards and good draw engine.
It's a 'natural' counter vs decks like Handlock, Giant/Freeze Mage, Miracle Rogue and any other deck based on combo, due to it's ability to burn enemies' cards.
No matter what cards you've got in your hand, they can almost always synergize well with those that are already on board or the cards that you're going to draw in next turns.
It's difficult to classify this deck, because there are many ways to win.
It depends on cards you draw and your opponents' plays and win conditions whether you go all in and rush him, play a control match and eventually outvalue him, burn his combo cards, or finish him with your own combo

THE PLAYS:

Naturalize - Most often used in late game, for big minions. Nevertheless it can work wonders in early game aswell, for example: when you've got advantage in first turns, then opponent coins Yeti at turn 3 -the answer is Naturalize+King Mukla. The advantage on board that you get is so tremendous that even those 4 cards your opponent got won't be enough for him to make a comeback.
Synergies: Sylvanas, King Mukla, Coldlight Oracle; partially: Nerubian Egg, Dancing Swords.

Undertaker - No need to explain, best turn 1 play. Turn 2 - play a minion with deathrattle and trade Undertaker with a 2 mana cost minion. It's also possible to create a big 1 mana minion in late game.
Synergies: About 3/4 of cards in this deck.

Bloodmage Thalnos - Although there are only 3 spells in this deck that scale with spell power, its still very useful. It allows to kill a 3/2 minion with Wrath and still draw a card.
Other scenario: Opponent didn't play minion on turn 2 -> play Nerubian Egg then at turn 3 - coin, bloodmage then Wrath the Egg.
Synergies: Swipe, Wrath

Cult Master - This overlooked card is a gem of this deck. It allows you for enormous draw with Force of Nature, Onyxia's whelps and other minions. And who expects a Cult Master?...

Keeper of the Grove - Turn 2 Nerubian Egg, turn 3 - coin, Keeper and use a Moonfire on the Egg. Other scenario: turn 3 Dancing Swords, turn 4 silence it.

Soul of the Forest - Using this spell a turn after playing Onyxia wins you a game if opponent can't kill the whelps before.
Other scenario: have 3 minions on board, then play Rivendare, Soul of the Forest and trade the minions. Next turn you've got 7 targets on board for Savage Roar.
Also amazing when you've got Rivendare on board, then play Force of Nature + Soul of the Forest the same turn.

Possible other picks:
- Cenarius
- 2nd Swipe
- Millhouse Manastorm
- Youthful Brewmaster
- Sunfury Protector/Defender of Argus
- Big Game Hunter
- Abomination