Hearthpwn

Great tempo rogue deck that has worked well for me so far. 

Mulligans & Matchups:

vs Rush: You want to get AoE such as Blade Flurry, FoK etc.. & other removal like deadly poison. Aim for board control early game and then rush them down when they start running out of steam. This deck somewhat struggles vs Rush, but you can still win after some practice. Be smart with your removal & try to get the most value out of each spell.

vs Control: Removal like deadly poison, sabotage, eviscerate etc.. & early-mid game monsters like Si-7 Agent. You will want to try your best to keep up with the enemy & gain board control. Rogue has very powerful removal & combos. So use that to your advantage. At turn 6, you can summon Trade Prince Gallywix. This guy is very strong and he'll snatch you some good removal spells. Keep the tempo, but also try to play around removal. Remember that this is a tempo deck & that you should not try to out-control your opponent the whole game. Make smart trades & good tempo plays.

Card choices & Replacements:

Sabotage:  Amazing removal that also can destroy your opponent's weapon. You can replace this with Assassinate, but I don't really recommend doing so.

Bloodmage Thalnos: This is a very high-value card. He is like Loot Hoarder + Kobold Geomancer. You can replace him with either of the two cards previously mentioned.

Big Game Hunter: BGH has saved me many times against decks like Handlock & Warrior. It is especially good right now because a lot of decks run Dr. Boom. If you feel like you don't need BGH, you can replace him with another 3 drop, such as Earthen Ring Farseer.

Harrison Jones: I've noticed that I face against a lot of decks with weapons. With the new Luster for Battle (Paladin), Powermace (Shaman), Glaivezooker (Hunter) etc.. you will want a card to remove those weapons. HJalso helps against Handlocks (Jaraxxus) & Warriors. He can be replaced by a removal spell, Sylvanas or Cairne.

Trade Prince Gallywix: This is one of the best class Legendaries from the GvG expansion! He is very useful because he causes enemies to think twice before casting a spell. When they eventually decide to use a spell, you gain a copy! Even if a Mage Polymorphs him, he still gets lots of value. The Mage spends a removal spell + you get a copy yourself. Gallywix can be silenced, but he is still a 5/8 body.  A combination of a 5/8 body & a one-way Lore Walker Cho ability makes this one of the best Legendaries in my opinion. I highly recommend getting him. A somewhat decent replacement is Loatheb.

Dr. Boom: There's not much to say about this guy. He's OP & that's about it. He can be replaced with Sylvanas, Cairne Bloodhoof or Kel-Thuzad.