Hearthpwn

EDIT: Removed the Scientists and the Duplicates because it just made the deck a lot slower than it felt comfortable. Even though those duplicated Flamewakers felt good, they just require too much mana to be played again. 
Removed Sludge Belchers, Flamestrike, and the Pyroblast as they seemed too chunky, and slowed the game a lot, leading into a dead lategame. Flamestrike was mostly just a call for help in an already dead late game, and the Pyroblast was a dead card in most cases, even though it's an incredible topdeck. 
Added a Polymorph for them big threat removals and Water Elementals and a Snowchugger for mid/early control and because the synergy with Ice Lance is too good. Controls them pesky warriors, paladins, rogues and hunters too. 

EDIT 2: Wanted to try out a more aggro version of this deck and it seemed to be even better than the one I had in mind. Took out Loatheb to make it more aggro and one Flamecannon as it can get pretty stuck of a card sometimes. Added Clockwork Gnomes as they proved to be really amazing with the 1 mana spell they leave behind. I will leave a detailed description on the spare parts as soon as we hit our goal! I added a Loot Hoarder as it's a good card draw card. I want to keep this deck low cost, but if you have the Bloodmage Thalnos, use it! 

EDIT 3 : The deck has been changed to fit the current meta which is full with all kinds of warlocks warriors and hunters! The Ice Lances have been removed as the late game cards might show more consistency and you might not experience the synergy with Frostbolts that much. The Water Elemental and Polymorph have been removed to make space for minions that give you a Spare Part to fill up the spell pool for our spell-hungry minions. 

Warlock: 3-0
Warrior: 2-0 (both control)
Hunter : 2-0 
Druid: 2-1
Mage: 2-1 
Rogue: 1-0
Priest: 1-0
Paladin: 1-1

Tirion Fordring
Mogor the Ogre
Gruul
Hemet Nesingwary
Ysera
Ancient of Lore
Ravenholdt Assassin
Nerubian Egg
Defender of Argus
Master of Disguise
Argent Commander
Axe Flinger x2 (got one against a Face hunter, was mega fun) 
Druid of the Fang
Warbot
Unstable Ghoul
Tinkertown Technician
Mana Wyrm (who said we can't have enough of them?)
Thrallmar Farseer
Gnomish Inventor
Succubus
Lord of the Arena
Windspeaker
Kobold Geomancer (helped me get a 5 damage Flamecannon into a belcher

The mulligan for this deck is very flexibile and versatile, most of the things in this deck are very good, low cost and might make you think you should leave them in your hand. That's where you will probably be wrong. The first thing that you need to realise is that if you don't have the coin and are playing first, you are gonna have a much harder time than when you have the coin. The Coin is a spell that perfectly fits with Jerry. I will explain that further in the strategy section. 

As in my previous guides, I will setup a general mulligan, which will be refered to as Gen.Mul. in the following guide. The General Mulligan for this deck would be (left = more important, right = less important):

With Coin: Jerry (Flamewaker) ,  Sorcerer's Apprentice, Clockwork Gnome, Arcane Missiles, Mirror Image, Mana Wyrm, Frostbolt, Flame Cannon. 

Without Coin: Mana Wyrm, Clockwork Gnome, Sorcerer's Apprentice, Arcane Missiles,Frostbolt, Mirror Image, (Flamewaker) Jerry. 

Control/Midrange Decks (Control Warrior, Dragon Warrior, Tempo Mage, Midrange Hunter, Control Priest, Oil Rogue, Combo Druid, Freeze Mage, Handlock, Grim Patron Warrior): Try to go for Gen. Mul. The cards that you might also consider keeping are the Unstable Portal and Arcane Intellect as you have more space and there isn't that much pressure on your face early on. 

Aggro decks (Face Hunter, Mech Mage/Warlock/Shaman, Face/Ebola Paladin, Hybrid Hunter, Zoo Warlock): Go for Gen.Mul., minions are more important than spells here. Definitely no space for Unstable Portal, ditch that, Mirror Image plays a big role. Arcane Missiles even bigger. 

EXCEPTIONS: Against hunters, mages and warriors the Flame Cannon plays a big role in early game removal, and should be left at ALL costs. Easy removal for other Jerries, Armorsmiths, Frothing Berserkers and whatever comes out of the Animal Companion. I usually keep the Kezan Mystic against hunters and mages no matter what. 

Justification: When you have the coin you want to get as many spells ready for Jerry as possible and you want to use as least as you can until turn 3 for that special Jerry Combo, while early minions are also important as you will play them until turn 3. (More in strategy)
When you don't have the coin, you just need to try and get a curve for yourself, which is done best with the Mana Wyrm/Apprentice/Gnome. 

The PERFECT draw and play would be T1 Clockwork Gnome/Mana Wyrm T2 Sorcerer's Apprentice T3 Jerry (Flamewaker) T4 LOAD THE CANNONS JERRY! (use free/discounted spells until opponent ragequits)

As the tempo of the deck changes drastically with the Coin, I will divide the early game strategy into two parts:

EARLY GAME

With the Coin: When not facing anything too quick in early game (see Control Decks above) and having Jerry in your hand you want to wait for that turn 3 sugar sugar with Jerry + Coin + 1 Mana spell. Patience is a virtue. On turn one in that case I would say the Clockwork Gnome is better as it gives you another 1 mana spell and the Mana Wyrm requires spells to be played to it's fullest so I like to keep it for mid/late game in this case. Ultimately, the Sorcerer's Apprentice survives and you get free spells for Jerry. (WARNING: BIG CHANCE OF ORGASM AND HIGH FIVES FROM ALL KAPPAS)

If you don't have Jerry in your starting hand, and you are facing aggro, pray to RNGesus to those removal spells like Arcane Missiles, Frostbolt and Flame Cannon. Mirror Image helps a lot as well. 

Without the coin: This is the less favorable situation for this deck. Here you have to try and get that early curve or else you are not going to have a very good time. It's far away from a lost game, as there are enough cards to remove and to stall the game, until a better chance arises. Having the Sorcerer's Apprentice surviving is pretty much like having the Coin, so you can understand why Mr. Jerry gets a hard on when he sees the Apprentice on the board. Who said demonic nagas and gnomes don't go together?

MID AND LATE

As the midgame comes by, you want to start thinking about getting some of the heavier minions out. The Mechanical Yeti is one of the best choices here as it gives you another Spare Part to use with Jerry, Mana Wyrm, or ultimately, Archmage Antonidas. Boosting Mana Wyrm or Jerry with spells is also more than wanted, which rounds up your mid game. Mid game is where most of the decks get their brightest shine in the current meta, so removals like Fireball are usually really important.

Turn 5 is the turn for our Azure Drakes, which are perfect for card draw and those sweet 4 damage Arcane Missiles. Careful, Jerry might get a hard on again. Sylvanas on turn 6 is in most cases a game winner, especially when facing stronger decks like Handlock, and afterwards come Dr. Balanced on turn 7 and Ragnaros on turn 8. If Archmage Antonidas is present in the hand, you might want to save some Spare Parts and low cost spells for him. Try to not play him on turn 7, as it gets targeted by every single possible removal spells from your opponent. Best case you want to play him as late as possible with as many spells possible at the same time. If you are writing down what your enemy used and you are sure Antonidas can't be removed, and Dr. Boom is taking a vacation, play him. But only in that case. By then your opponent should be dead from the spell burst, Ragnaros the Firelord's passive or the Fireball spam from the Archmage.

Cards like Arcane Missiles, Sorcerer's Apprentice, Mana Wyrm,Frostbolt,Fireball, Flamewaker Jerry and Arcane Intellect I believe are mandatory and self-explanatory. Dr. Boom is in the deck cause OP. 

2 Mirror Images - A lot of people are running only one. I believe that two are really good as it give your Mana Wyrms or Apprentices a lot of space  against all kinds of decks. 

Clockwork Gnomes - I believe that they are very important in keeping the early game in check. Spare Part is always lovely, and with Sorcerer's Apprentice's help, can become very deadly for the enemy, and also make your Archmage Antonidas stealthed on turn 8, which is usually an instant game win. 

Kezan Mystic - A tech card whose importance varies on the ladder with the shifts of meta. A crucial card against all these hunters and mages present in the beginning of S15. Should be changed with a Water Elemental if Oil Rogues continue gaining on popularity. 

Mechanical Yetis - Probably the card I will get most trash for. Why not Piloted Shredders? Why not Water Elemental? Say that to my Archmage Antonidas with Finicky Cloackfield on. Also, not as easy to remove as one might think. 

Sylvanas Windrunner - With this meta full of Handlocks and fat minions, Sylvanas solves all issues. Be careful how you handle her, and she will give you a very strong minion. 

Ragnaros the Firelord - Works like a stupider version of an 8 attack Ogre charge. Incredibly lethal and efficient if the board before him is cleared. The card is a Big Game Hunter target, true, but even before one uses a BGH, he will deal 8 damage to whatever he has in front of him. Works perfect with any deck except ones that run an Imp-losion. That shit has to be removed asap if your Ragnaros is on the board. 

Lack of Mad Scientists & Secrets - I am pretty sure I have seen a Kezan Mystic in almost every deck that I have encountered so far. Losing a secret just hits your head way too much. If the meta changes and cancer hunters die out as they should then I might consider getting some secrets rolling. Right now I am satisfied with this version, as it works perfectly. 

I will not mention all basic and common cards as I believe that everyone, or most of people have them, I will include some rares as some people might've disenchanted them or something like that. Scratch that, why would you DE Unstable Portal? It's one of the most fun cards in the game. Jerry is irreplaceable.

Unstable Portal -> Arcane Intellect/Polymorph
Sylvanas Windrunner -> Piloted Sky Golem
Ragnaros the Firelord/Archmage Antonidas/Dr. Boom ->Pyroblast/Flamestrike/Water Elemental/Toshley

Note: Don't think to expect such good results if you swap out many cards out of this deck.