Hearthpwn

As you can see from the deck list, the aim of this deck is to swarm the early board with murlocs, while building for a deadly finisher combo.

At the time of writing, the most prevalent aggro deck on ladder is currently Murloc Paladin, so the Hungry Crabs are amazing. 
But even if you don't face Paladin, then you can still make good use of the crabs with Fish Flinger or even on your own murlocs - I can suggest using it on Murmy
The crab is a huge tempo swing in your favour against murloc decks.

For the mid game, just keep the tempo up and look to try and get the opponent down in health. Use the Fireballs and murlocs to keep control.

You then have the option of looking for 2 specific combos to go off with:
Khadgar and Power of Creation (or Tortollan Pilgrim) 
or
Naga Sand Witch and 2 x Pyroblast

Both of these are devastating finishers and I've been surprised at how consistent they are. If you don't get much useful from the Power of Creations, you still have a fallback plan. (Or 3...)

Let me know how you get on.