Hearthpwn

So far I have a 68% win rate with this deck after 25 games and I'm still trying to figure out which cards work or not, so feel free to change the deck list.

Mulligan: 

You want to use all of your mana in the early game so you have time to pull combos and to have threats already. Always keep at least one drop as you can buff and keep your two drop uncontested if you trade with another one drop. If you want to play greedy you can keep the combo of Street Trickster and Imp-losion

Match Ups:

This deck loses to most control decks really badly so mulligan aggressively with cards that stay on the board like Voidcaller so you have a chance of pulling Doomguard or Lakkari Felhound from life tap and Imp Gang Boss because it is a sticky minion that can combo with curve Crystalweaver.

Against other aggro decks or zoo like decks getting a Voidwalker with a curve Demonfire can give enough control for two or three turns.

Going second for Aggro or Control you want Imp Gang Boss because it can help you catch up on board or keep one drop with Bloodfury Potion as that can also allow you to catch up on board. Keep Demonwrath if you hand is slow or weak   

Classes that have early game removal keep buffs and minions with 4 or more health, but still keep your one drop if they don't have the removal. Go face a lot more against control mage, paladin, warrior, priest as you can run out of steam easily and need to outrace board clears

Against hunter or aggro classes play control so you don't loose on board or die to burst

Win Conditions:

Getting control of the early game with buffs and combos allows time to buff a demon to a large size or buffing a good size board with Crystalweaver so you can do a lot of burst damage and your opponent has to deal with your board or your buffed demon

Cards that you can remove:

Flame Imp can be a dead draw and it deals damage to you so you can remove one and add either Mal'Ganis or Lord Jaraxxus and this applies to Lakkari Felhound as having multiple discard cards adds more dead draws with out Voidcaller.  Darkbomb can replace Mortal Coil as it can be more flexible and be burst while Mortal Coil isn't that strong in a control match up