Hearthpwn

I think this is the best deck to the current time to mount legend.
This deck against all the decks of the moment : 

Mulligan :

 Match up : 

[65/35] Versus Druid Double combo or Ramp

[50/50] Vs Druid Aggro : The winner will be the first player you play Dr. Boom or Fel Reaver +  Keep the Swipe

[60/40] vs Mage Freeze

[45/55] vs Mage Tempo

[65/35] vs Secret Paladin ; Yes you can counter easely this "awesome deck is the secret paladin" +  Keep the Swipe

[35/65] vs Mid-Range Paladin : it's 80% loose if he play Reno Jackson or Big Game Hunter

[35/65] vs Priest : it's hard if he have Entomb

[50/50] vs Oil Rogue

[50/50] vs Aggro Chaman

[65/35] vs RenoLock or MalyLock

[40/60] vs ZooLock : Keep the Swipe

[40/60] vs Control Warrior

[60/40] vs Aggro Warrior

[55/45] Vs Aggro/MidRange Hunter : Keep the Swipe

 

Legend :

 74.5% Winrate [Rank 4 to legend] 35W - 12L

 Good Luck !