Hearthpwn

Took this deck to legend. Pro streamers have been playing it at high ranks.

Mulligan:

Look for Mecharoo, Galvanizer, Upgradeable Framebot, and Ursatron. If you have a solid curve, keep Replicating Menace. Venomizer and Spider Bomb are not bad keeps either. 

Playstyle: 

This deck is an aggro version of the Mech Hunter archetype seen in the meta. Thus, we go face, while maintaining board control. If we lose board control, this deck has almost no comeback mechanics so do not lose board control. One of our best comeback mechanics is Venomizer and Missile Launcher combo. 

The deck revolves around creating big mechs with magnetize, and smacking face. Using tools such as Venomizer and Spider Bomb to make smart trades is important. Fireworks Tech is an amazing card in this deck, and has huge potential with cards like Mechanical Whelp. Wargear is great for pushing face damage. Houndmaster Shaw helps with board control. Boommaster Flark provides more face damage. Besides its obvious uses, Mossy Horror can be used to trigger your own bombs.Throwing down Explodinator gives three magnetize targets! Upgradeable Framebot is a hard to remove turn two play that you can magnetize for high health minion.

Matchups:

Druid: We mostly see Token Druid. Even matchup. Board control is necessary, Mossy Horror is a lifesaver. If you have a good start consider keeping cards like Mossy Horror and Missile Launcher in mulligan phase. Token Druid only has Swipe for single target removal, so if you can build a large mech with magnetize and keep it alive (know how much damage the druid can do to it), you can get an easy win. 

Hunter: Even matchup. Just play regular playstyle.

Mage: Against Khadgar mage, we need to kill them before late game. This is your BEST matchup, when you see mage, just go face. Remember, their early game is non existent besides the 3/2 on turn 3, and they do not run Polymorph.

Priest: Similar to mage, we are favored. Nobody really plays priest though.

Shaman: Murlocs is bad matchup...board control is how we will win.

Rogue: Another tough matchup. Play around Sap, that kills your chances of winning. Try to flood the board, most rogues do not run Fan of Knives. 

Warrior: Hunter has always done well against warrior, go face but watch out for Warpath and Brawl.