Legend Proof: https://imgur.com/7d4nFur
5 Upvotes - General Overview and Strategy 10 Upvotes - Mulligan Guide 15 Upvotes - Tech choices and Card Replacements 20 Upvotes - In-depth Matchup Guides
General Overview and Strategy:
This is an aggressive deck that looks to establish a strong early game board and snowball the game. Against slower decks, try to push damage early on since you have plenty of burst potential in the mid-late game with Leeroy Jenkins, Cold Blood and Shadowstep. You often want to try and control the board early on by using efficient removal such as Backstab and SI:7 Agent. Keeping a few minions on board will help you transition into a powerful mid-game due to powerful buff cards such as Cobalt Scalebane. At times, you may want to consider not playing any pirates until turn 3, if you have Southsea Captain in your hand, as you can bring out a 2/2 Patches the Pirate.
This is very straightforward. You want to mulligan aggressively for Prince Keleseth, while keeping at least one 1 drop. Fire Fly and Swashburglar are cards you would usually keep. Against aggressive decks, consider keeping Backstab for early game removal. Never keep Shadowstep unless you already have Prince Keleseth in hand.
Tech Choices and Card Replacements:
Shaku, the Collector - If you have the dust to craft him, Shaku can be a powerful 3 drop due to its ability to generate value over time. More importantly, he has stealth which often allows him to stick to the board and receive buffs from various other cards in your deck such as Bonemare.
Xaril, Poisoned Mind - Another card that you could add if you already have him or have the dust to craft him. His value lies in his ability to generate cheap 1 mana cards which can be conveniently used to activate combos. These cards can also let you draw to cycle faster or give a minion +3 attack for more burst. If you're keen on including him, I'd recommend replacing Naga Corsair purely due to the number of Golakka Crawlers on the ladder
Leeroy Jenkins - If you don't have this card, your deck's burst potential is going to suffer quite a bit. But, adding in tech cards such as Spellbreaker can give you a much smoother mid game, as you won't have a Leeroy dead draw. Bittertide Hydra is another powerful 5 drop that can win you games outright if left alone. A slightly less optimal replacement for Leeroy would be Reckless Rocketeer, as it achieves the same purpose, except it's 1 mana cost higher.
Hallucination - This is more of a hit or miss card that can sometimes grab you wins while other times get you nothing. I would mainly consider running this if you find you're having trouble activating combo cards.
Deadly Poison and Shadowblade - These are mainly tech choices against a heavy aggro meta where you need the extra early game removal. If aggro decks are a problem, consider also replacing Plague Scientist with a 2nd copy of Tar Creeper.
Vs Priest - Most priests you encounter will be the Razakus variant. In these matchups, you have to play aggressively, by pushing damage into their face whenever possibly. I wouldn't worry about playing around AOE in this matchup, as if you play slow to avoid AOE, you will lose in the long run. Keep in mind that if you can buff your minions to 4 attack, then do so as it will put them out of range of the various Shadow Words. Cobalt Scalebane will be your biggest friend against Dragonfire Potion. Apply pressure early through an aggressive board, then look to end the game with burst from Leeroy Jenkins and Shadowstep.
Vs Mage - Against tempo mage, try to control their board early and snowball the game through effective trades. Tempo mages struggle tremendously to come back against most decks when they are behind. Keep in mind their burst potential with Fireball, as you will sometimes have to avoid using your weapon to trade. The Coin will be your best friend when it comes to testing for Counterspell. Against quest mage, just push damage as fast as you can. Try to make the most of your hero power by chipping in damage every turn. If you reckon they're far from assembling their combo, then playing around AOE can provide for more sustained pressure through more minion threats.
Vs Hunter - Always trade with any beasts they may have on the board. Make sure you avoid allowing hunters to generate any board as they have plenty of buffs. Keep in mind Unleash the Hounds as it is their main comeback tool. By making efficient trades and keeping their board clear, you will make it very hard for hunters to generate any pressure. Consider keeping Backstab and SI:7 Agent (if you have the coin) in your mulligan for this matchup.
Vs Druid - Against Jade, you want to end the game early. Mulligan for an aggressive start and apply pressure by hitting face. Sometimes it's ok to leave up the jade golems, as druid has no way of buffing them and you want them to be the one making the trades while you deal face damage. Only AOE to worry about here is turn 6 Spreading Plague. Against aggro druids, look for early removal tools and control their board so they can't buff any minions. If they play Living Mana, it's best to ignore the minions (unless they have enough mana for Savage Roar) as trading will often put you too far behind and will provide them with more mana for the next turn.
Vs Warrior - For Pirate warriors, it's the same as any other aggressive deck. Keep their board clear of pirates so they can't make use of pirate synergies. Against fatigue warrior, you'll really want to end the game as soon as possible before they get enough mana to start gaining massive amounts of armour and cycling through their deck. In the odd case that your hand is full, beware of Coldlight Oracle overdrawing you. It's difficult to know whether to play around AOE or not in this matchup, as playing around AOE allows them to stabilise, while not playing around AOE might cost you all your minions.
Vs Warlock - Zoo is the standard formula for aggressive decks - keep their board clear while developing your own. Applying face damage early can be good as it will limit the number of times they can Life Tap, which will significantly reduce the threat of them drawing into powerful cards such as Doomguard. Against control warlock, there isn't much point playing around AOE considering how much they have. Pushing face damage is always good as most of their AOE will also damage them. Playing around Mortal Coil in the early game may help prevent them drawing into their mid-late game answers.
Vs Paladin - Same game plan as other aggressive decks. Control their board as they have a lot of buffs. If you run Spellbreaker, consider saving him for their turn 6 Spikeridged Steed. Vilespine Slayer really shines in this matchup against divine shield minions such as Tirion Fordring. Flooding the board will sometimes be good as it will likely deny them from playing Sunkeeper Tarim.
Vs Rogue - Against miracle rogues, only trade to remove important threats such as Gadgetzan Auctioneer. Pushing for face damage is crucial for limiting their options by applying pressure. Keep in mind that rogues have no access to healing so every point of damage is important. In the mirror matchup, whoever draws Prince Keleseth first has a much better chance of winning. Controlling their board in this matchup is also important for preventing potential buffs.
Vs Shaman - For Token shamans, the whole early game should be dedicated to removing any minion they play - this includes any totems they summon via their hero power. It's important not to overcommit early on with 1 hp minions as Maelstrom Portal can swing the game. Prioritise killing important threats such as Flametongue Totem, Mana Tide Totem and Primalfin Totem. Optimally, you'd want to have board control before turn 6, when they can go for a Doppel Evolve combo. If you are going to disregard their board to push for lethal, always consider how much potential damage they have with their current board and Bloodlust.