Hearthpwn

Pretty standard deck and helped me climbed ladder rather quickly in the lower ranks. Goblin Blastmage is great against secret paladins and face hunters and Mechwarper ramp can seal the game vs. control matchups.

Unstable portals are thrown in there rather than secrets, since portals can be game winning whereas secrets in this aggro meta sees weak play while control classes play around it (doesn't help when some hunters run flare and secret paladins has, well, secret keepers). Unstable portal as long as you get at least a 2 drop, you're getting some value. There's one particular game against Freeze Mage where I drawn into Alex and won by turn 8 as Alex did roughly 10 damage to them on turn 6. Unstable portal is impossible to play around and will earn you some wins.

General mulligan:

Always keep mechwarper, cogmaster, manawyrm, annoy-o-tron, clockwork gnome. Keep flamecannon if non-aggro (warriors, priests, mages). Only keep frostbolt for druid and mage. Keep snowchugga against warriors, hunters, and paladins. Consider keeping Loatheb against warrior or priest.

Unstable portal should be thrown away against aggro since it's too variable to play on turn 2 especially if you have no turn 1 play. I'll keep Unstable if you have Mana Wyrm already. Playing on curve is usually the ideal but consider saving blastmage for 1/1 swarms.

General playstyle:

Against aggro, board control is more important. Against control, go face most of the time. You'll get rekt by board clears but you'll also win the game if they don't draw into it. I wouldn't play around board clears since they require that one card to win, when your chances of winning decreases if you choose to play around board clears. This deck doesn't have antonidas or card draw so you'll eventually get outvalued against control/midrange decks if you play around board clears.

Tech choices:

1. Clockwork Knight. One is used over 2 Fel Reavers for consistency. Fel Reaver is always a gamble to play and this deck is quite low in RNG other than Unstable Portals and drawing into Fireballs.

2. Unstable Portal. Unstable portal is a card people can't play around. It can offer taunt, insane ramp, and you're usually decent as long as you get a minimum 2 drop.

3. Flamecannon. Matches really well against priests, warriors, and some druids. Usually can improve your win rates if you get it in opening hand against these classes.