Hearthpwn

• Backstab - Mana efficient early-game removal, which allows you to destroy an opponent's minion and play one yourself on the same turn. It also serves as a great combo enabler for SI:7 Agent and Eviscerate. Should not be substituted.
• Deadly Poison - Works well as early-game removal, as a board clear with Blade Flurry and for burst damage in the later stages of the game. It can also serve as a combo enabler, especially good with Tinker's Sharpsword Oil to guarantee that the buff hits a minion that can attack. Should not be substituted.
• Sap - Often used as "Your opponent skips their last turn" for 2 mana, Sap is a great tempo card as it lets you get rid of big threats for very little mana. The best use is when you can also play a minion at the same time or to push for lethal damage through a taunt. Should not be substituted
• Acidic Swamp Ooze - Perhaps the best neutral basic card in the game. Provides a decent body for the mana cost and a big tempo swing if you can destroy a weapon with it. If you have Burgle, Preparation, Unrcity Valiant or Goblin Auto-Barber, then you can substitute this.
• Kobold Geomancer - Provides a spell power boost which is especially good for Fan of Knives, as well as a combo starter for things like Eviscerate and SI:7 Agent. If you have Bloodmage Thalnos then substitute this. Kobold can also be substituted for a Shiv, Goblin Auto-Barber or Undercity Valiant, but remove a Fan of Knives if you do so.
• Fan of Knives - A card efficient area of effect which deals with early game aggression. It's especially good with spell power. It can also be used to cycle through your deck if you're facing a control opponent. Can be substituted for Shiv or Goblin Auto-Barber.
• Gnomish Inventor - A card which provides a decent body as well as card draw. The 4 health gives it some survivability against aggressive decks, and control decks may waste resources getting rid of the body. Can be substituted for Sen'jin Shieldmasta if you face a lot of aggression, Tinker's Sharpsword Oil or Violet Teacher if you have it.
• Assassin's Blade - Can be used for removal for the first few charges, but really this weapon should be buffed and used for damage against control opponents. Particularly good against warrior to push for extra damage. Should not be susbstituted.
• Boulderfist Ogre - Used simply as a mana-efficient large body. One of the best neutral basic cards in the game. The high health allows the minion to stick to the board or used up removal/damage resources from your opponent. It can, however, be substituted for a number of cards since the card is mainly in there for its high value. If you have the Naxxramas expansion, then substitute Loatheb and Sludge Belcher. If you have Dr. Boom, then substitute this. It can also be substituted for cards like Shado-Pan Rider,Assassinate Preparation or Goblin Auto-Barber if you wish.
• Sprint - Essentially a 4-for-1. It allows you to cycle through a lot of your deck to find key cards like eviscerate or sap to be played on the same turn, or to find your combo pieces for the turn after. However, minions should always be played before this whenever possible since investing 7 mana is a big tempo loss. Great against control opponents. If you feel that it is too slow, then substitute a Shiv, Burgle, Tinker's Sharpsword Oil or Goblin Auto-Barber or any other card listed above.

1. 2x Azure Drake* - Azure Drakes provide both card draw, which allows you to cycle through your deck to find the finishing combo pieces; and sometimes much needed spell damage to boost you removal/damage spells (especially good with Fan of Knives and Backstab). On top of this, it also provides a small threat (Replacement: 2x Darkscale Healer)
2. 2x Eviscerate - Can be used as minion removal or enemy hero damage, making it a very versatile spell. Paying 2 mana for 4 damage (or more with spell damage) is really efficient for a damage spell (compare to Shadow Bolt) and at a low cost of 2, it's relatively easy to combo. (Replacement: 2x Bloodfen Raptor)
3. Tinker's Sharpsword Oil - This is mainly to be used as a finisher, but can also be used to clear the board with Blade Flurry (Replacement: Stormwind Champion)
4. 2x SI:7 Agent - SI:7 Agent's can give you amazing tempo when played alongside your Backstabs or Deadly Poisions (or even the Coin) in the early game, often killing 2 minions for very little resources while developing a 3/3 minion. It's a value card, so try to use it to destroy minions, rather than to deal damage to the enemy hero. (Replacement: 2x Chillwind Yeti)
5. 2x Blade Flurry - Blade Flurry is way of both clearing the board and dealing damage to the enemy hero. This should be used alongside your weapon buffs or the last charges of your Assassin's Blade in order to maximise the value. (Replacement: Acidic Swamp Ooze + Assassinate)
6. 2x Earthen Ring Farseer* - The Rogue class in general relies a lot on its hero power and other weapons to control the board, and this means taking more damage than other classes would. Farseers allow you to heal up a reasonable amount while developing a 3/3 for a low mana cost. (Replacement: 2x Shattered Sun Cleric)
7. 2x Piloted Shredder* - Piloted Shredder is hailed by most as the best 4-drop in the game. Its body provides a small threat to the opponent and the deathrattle means that you are more likely to have a target for the Tinker's Sharpsword Oil combo. It's a very replacable card, however, since it's just there to provide board presence. (Replacement: 2x Sen'jin Shieldmasta)
8. Southsea Deckhand - At a low mana cost, it's a good card to use to activate any combo pieces (as long as you can get value from the charge), in particular the Oil combo since it also provides a charging target for it. It can sometimes be used as 2 damage removal or to counter hunter and mage secrets. Try not to use the card without a purpose or to just deal 2 damage to the enemy hero since it will use a lot of it's value and combo potential. (Replacement: Shiv)

*These are great neutral cards that work in almost every deck. If you are planning on playing other mid-range/control classes, then I would put these higher up the crafting list.

Against Paladin and Hunter, it's a good idea to keep Fan of Knives, since it deals really nicely with Muster for Battle, Haunted Creeper, Leper Gnome and other low-health, swarmy creatures.

Earthen Ring Farseer is also a good keep against these aggressive decks as it guarantees some heal. You can expect Shaman opponents to be playing a mech deck, which is also aggressive.

Priest has a hard time dealing with 4-attack minions, and it's a slow match-up, so keeping your Azure Drake and Piloted Shredder can often be beneficial. Priest is a very favourable matchup, but one way of losing is to a turn 3 Injured Blademaster + Circle of Healing combo. This is easily dealt with by keeping a Sap.

Warrior and Druid also have a hard time dealing with Piloted Shredder effectively, so it's a good keep against those decks. Make sure you have a good turn 3 play against Druid, however, since you win by maintaining high tempo. Assassin's Blade is also a good keep against Warrior since it pushes for lots of damage.

The Rogue match-up is often decided by who manages to draw their damage first, and for this reason Gnomish Inventor and Azure Drake are OK to keep. Note that for weapon classes like Rogue and Warrior, Acidic Swamp Ooze is good to keep, but make sure you hit a weapon.

A lot of the Warlock opponents will be running Zoo decks and most of the Mages will be of the tempo variety. Against these, it's important to keep clearing the board, and a Blade Flurry helps as long as your also have a Deadly Poison to go along with it. Try to have a play for each turn as these will be a fast match-ups.