Hearthpwn

Strategy

It's a pretty easy win if you play your cards right and make the right combos at the appropriate time.The two most important cards in this deck would be Explosive Trap and Unleash the Hounds. It's pretty self explanatory, those cards pretty much won me the game, although I have to admit I was lucky, I got both of them very early on in the game. Hungry Crabs and Powershots are also extremely useful. You'll generally be fine as long as you don't let his Murloc Tidecallers get out of control. Make favorable trades with your Unleash the Hounds if you get the chance and this shouldn't be too hard.

The Unleash the Hounds and Scavenging Hyena combo is one easy way to get massive damage to his face, especially if you have a Knife Juggler on the board already, after one of these combos his side of the board should pretty much be clear or close to it. Remember, prioritize the removal of his  Murloc Tidecallers.

While you're taking out his  Murloc Tidecallers, you can be buffing up your own, another way to make Giantfin take a lot of face damge, just be careful not to kill your own minions with your Dreadscale. 

Go for face as much as you can and let your removal cards like Explosive Trap, Powershot, Dreadscale, Hungry Crab, Quick Shot, and a little helping hand from your Knife Jugglers take care of his minions. 

Mulligan for Hungry Crab, Leper Gnome, Murloc Tidecaller, Glaivezooka, Knife Juggler, Mad Scientist, Scavenging Hyena and Dreadscale. If you get Explosive Trap or Unleash the Hounds that's fine too because you'll be needing them soon. 

Summary

Like I said, go for face as much as you can, buff your Murloc Tidecaller and Scavenging Hyena for major damage to his face, keep his side of the board in check with your removals and don't let him buff up his Murloc Tidecaller. Explosive Trap and Unleash the Hounds are key cards for removal and to clear his board. With all this you should do fine! Let me know how it goes and good luck!