Hearthpwn

Update: Do not play this deck if you are facing lots of Reno priest.

This deck does not run combos like

Dollmaster Dorian + Plot Twist + Kael'thas Sunstrider + Cataclysm

or

Drakkari Enchanter + Emperor Thaurissan + Mecha'thun + Cataclysm

Pros：

1) This deck is cheap...

2) To set up for lethal, you can play Emperor Thaurissan when any of the four cards are on hand: Mecha'thun, 2*Plague of Flames, Dark Pact. It is very flexible in terms of both mana cost and wining conditions.

3) This deck cycles pretty fast, with all these low mana cost minions and spells, you can expect to dump all of your cards by turn 14 or 15.

4) Tones of heals, as well as a lot of removals (AOEs), works pretty well against aggros.

Cons:

1) Based on my game experience, turn 14 or 15 lethal is very common, almost unable to make it faster than this. Other Mecha'thun warlock decks that run combos may have a much faster win in some extreme cases: turn 6 Hemet, Jungle Hunter into turn 9 combo win. 

2) Have trouble dealing with big death rattle minions such as Carnivorous Cube, Enhanced Dreadlord and Scrapyard Colossus

3) Really rely on the single card Emperor Thaurissan, if it's the last card on the deck, we need to plan very carefully.

4) If your opponent knows what cards you are playing, it is possible you won't be able to dump spells out of your hands, especially those which need to target a minion. (unlikely to happen unless you have been playing against him many times)