Hearthpwn

As anyone who's laddered will tell you, after about rank 5-15 you hit an face/aggro dead man's land.  People are just grinding through this and are looking for the fasted way to get there that they can.  Zoolock, aggro-hunter, and mech mages are by far the most common match ups I see.  I decided to throw together a deck that's completely tech'd into destroying those aggro decks.  I used some cards that are pretty dead against mid-range and control (Explosive Sheep and Deathlord) but really shine against aggro.  

The Deathlord will generally trade for 3 cards or heavy duty spells like Fireball.  Aggro decks run little to be afraid in terms of what it can pull out.

The sheep are a great early drop to really burn down early drops.  It shines mid and late game against aggro as well since their cards tend to run little in the way of life.

Dr. Boom and Rag are your standard finishers and also help maintain board control even when they 'miss'.  

You'll always want to mulligan for early removal like Backstab and Deadly Poison.  

Mech mages you want to fish for your blade fury + deadly poison combo.  They tend to hyper-extend their first 3 turns and dump their hand.  You can cripple them badly with a well timed board clear.  It's not uncommon to take out 4 or 5 minions on turn 3. 

Don't be afraid to get your hands dirty taking things out with your weapon to control the board.  You have some decent life gain in the deck and you'll cycle throw it fairly fast with some decent draw power.  

Prep is going to often be used for sprint but can also feed into Sharpstone Oil to set up a huge Blade Fury or just buff up your dagger and weapon enough to take out bigger minions.  It can also be a pretty steady win condition.  

Once again, this deck is designed for ladder climbing in a heavy aggro environment.  The higher win% means you'll climb fairly quickly.