Hearthpwn

Hi all. Been having fun with this. You can adjust the battlecry tech based on what you see most/cards you have. Great video guide by Darkseeker below as well!

Tech and subs:
I went Chief Inspector because I've been running into a ton of secret mages. Horde Operative can be used instead of Chief Inspector if you want lower curve and to steal instead of destroy the secrets (great vs. Ice Block).

Gluttonous Ooze vs. weapon based decks, can be swapped for Acidic Swamp Ooze if you want a cheaper option. Kobold Stickyfinger is an option too but it costs more. If you aren't running into a lot of weapons then use The Lurker Below which is great vs. aggro. Barista Lynchen, Instructor Fireheart, Jepetto Joybuzz, or Grumble, Worldshaker can be used for more value. Grumble and Barista builds are greedier and aim for infinite Shudderwock as win condition, these tend to be better vs. control and worse vs. aggro. 

Shudderwock: Cast when you can get good value. Often a few battlecries is all that is needed to close out game. You don't have to always go infinite or wait for 20 battlecries. A lot of new people save this card for infinite combo (cast Zola the Gorgon earlier in game and then Shudderwock with your board empty to get new Shudderwock in hand. Repeat forever). Generally you want some combination of the battlecries from Zephrys the Great, Boompistol Bully, Loatheb, Mutanus the Devourer, Reno Jackson and Kazakus, Golem Shaper at least before casting Shudderwock. The specific battlecries you need vary with each matchup, so knowing the opponent's goal helps you determine what battlecries you need to have played before casting Shudderwock to disrupt opponent's game plan. 

Battlecries: 

Boompistol Bully: You want this battlecry so they don't Zephrys the Great, Keli'dan the Breaker, Flik Skyshiv, or Firemancer Flurgl + Toxfin your Shudderwock board. Great against battlecry heavy decks like secret mage, and other highlander decks like LPG mage, Reno Shaman, Raza priest, Control Warlock, etc.

Loatheb: You want this battlecry vs. any control deck so your Shudderwock board doesn't get hit by Psychic Scream, Twisting Nether, etc. 

Doppelgangster: This battlecry duplicates Shudderwock

Kazakus, Golem Shaper: Battlecry usually duplicates Shudderwock. Great tempo card too. I usually go for a 5-cost golem but this can vary based on the state of your game. Battlecries you want from the golems are duplicate, do x damage to y enemy minions (vs. aggro), freeze x enemies (vs. aggro), polymorph x enemies (vs. control), etc. 

Dirty Rat and Mutanus the Devourer: These battlecries are great vs. control and combo decks like Warlock, Mozaki, Raza Priest, etc. If you can eat or Dirty Rat a Tickatus, Raza the Chained, or N'Zoth, the Corruptor it can win you game. With Shudderwock and Zola the Gorgon you can get up to 5 battlecries from dirty rat and Mutanus

Chief Inspector: You want this battlecry (or Horde Operative) vs. any secret based deck

Reno Jackson: If you Reno against aggro it is usually an autowin. Then repeating this battlecry with Shudderwock is killer. Most aggro decks can't do >60 damage without running out of steam

Glacial Shard and Gluttonous Ooze: These battlecries vs. weapon based decks (Kingsbane)

Zola the Gorgon: You want this battlecry in control match ups to help Shudderwock go infinite if game goes on a long time. These are value based games. Usually not necessary vs. aggro. In aggro match just use it to get more value (second Zephrys or Reno for example)

Zephrys the Great: This battlecry is complicated. You will automatically receive in your hand one of the three cards that would have been recommended in the situation that you casted Shudderwock. This can vary by board state and hp remaining of opponent. If opponent is at 1HP for example you will likely get something that does 1 damage. If opponent is at 30 HP you might get Lord Jaraxxus. 

Lord Jaraxxus: Sometimes your hidden win condition. After you Shudderwock with 10 mana, Zephrys battlecry repeat from Shudderwock will often automatically give you Lord Jaraxxus. Opponent will need the turn after you Shudderwock to clear your Shudderwock board which gives you the turn after that to cast Jaraxxus without tempo loss. Then out value them with 6/6 Infernals until you win. The 3/8 weapon is nice too. 

Mulligans: Vs. Aggro you want Armor Vendor, Glacial Shard, Zephrys the Great, Ice Fishing, Primal Dungeoneer, and Reno Jackson. Sandstorm Elemental can be a keep vs. aggro as well (odd paladin, pirates, etc.) Vs. control keep Dirty Rat, Zephrys the Great, Loatheb, Primal Dungeoneer, and Ice Fishing. 

Defense: Healing Rain, Armor Vendor, Glacial Shard, Toxfin + Firemancer Flurgl + Ice Fishing, Diligent Notetaker, Dirty Rat, Maelstrom Portal, Sandstorm Elemental, Zephrys the Great, Lightning Storm, Primal Dungeoneer, Serpentshrine Portal, Tidal Surge, Hagatha's Scheme, and Gluttonous Ooze should help you stay in the early game vs. aggro. Reno Jackson as well. 

Diligent Notetaker + Healing Rain is an amazing combo vs. aggro or face decks. You can choose which spell you want to duplicate with notetaker depending on the match

Proof of Legend: