Hearthpwn

This is the version of this deck that has hauled me up to rank 5, from rank 25, and might still take me higher, depending how the season goes.  It's an original deck.

The plan:

1. Survive the early game:  The central feature of this deck is only available starting turn 9 (7 if you can get a Mechwarper to stick on 6), so your first goal is to make it to that turn.  You do this by A. Controlling the board, with cards like Doomsayer and Defile.  B. Healing whatever damage you can; Using, for example, Mistress of Mixtures and Lesser Amethyst Spellstone. C. Stalling for time, with cards like Giggling Inventor, and Bronze Gatekeeper. Zilliax can be any or all of the above, and more.  More on him later.

2. Play hard:  If it's not integral to your combo, fling it out like trash.  I often find myself ditching a doomsayer and a defile simply to clear up space in my hand.  This deck has a medium curve, with plenty of 1-2, but also 4-5.  Playing minions that cost 4-5 mana can get seriously challenging when you're trying to empty your hand as fast as possible.  Why are we emptying our hand?  We're doing it because of... 

3. Draw hard:  You need all the draw you can get, so that you're not left sitting while your opponent pulls out their own crazy combo.  I tend to have it in my head that if they have less cards in their deck than me, they're winning.  Counterintuitive, but true.  To that end, you want to be tapping pretty much as often as you can be.  Maybe that means using Bronze Gatekeeper and tap instead of Giggling Inventor.  Maybe it doesn't, it really depends on what you can get away with in a matchup.
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Now, we've talked a bit about how to run this deck.  Let's talk about how to win with it.

The combo that this deck was formed around was simple:

1. Coppertail Imposter onto a more or less empty board (Or at least one you can remove your minions from easily).

2. Next turn, Glinda Crowskin into 4 Mechwarpers, followed by as many Replicating Menaces as you need for lethal.  Then, hit them in the face, and watch the sparks fly.  This is why we packed Skaterbot, incidentally.  If they have taunts, Skaterbot means you can bust through.  Only 1, though.

However, there are variations on this.

For example, if you can get a Mechwarper to stick, you can fit up to 5 on board while still having space to magnetize in.  This means Zilliax and Wargear are also OTK options.  Or, if you just have an Annoy-o-Tron left from a Giggling Inventor, you can still do the OTK.

Alternately, if you're up against an aggressive deck that's got you up to the wall, specifically one that doesn't run full board clears (Twisting Nether and Brawl being two of the most prevalent I've seen) you can simply forget about needing a mech on board, as your board will not be cleared.  Better still, if you use the Zilliax combo, you also get a full heal, essentially crushing any aggro deck that decides to come for you.

Past a certain point, you begin to recognize stranger variations.

In general, you want to get a low early curve, often sacrificing any non-Glinda combo pieces in the mulligan phase to secure your initial survival.

Finally, just remember that you don't need 2 copies of any card for your combo, so if you want to, for example, drop a Mechwarper on 6 when the other one's in your hand, that's absolutely an option, and one that could even move your victory up a few turns, if you've gotten good draws.