Electra Stormsurge: I main shaman and this card is juicy! Every shaman player would love to have this card added to their deck!
Myra Rotspring: I love playing casino type in Hearthstone and this card really favors it a lot.
Zerek's Cloning Gallery: This card won't be great, but this is the main reason I'll start playing the priest for that, I never enjoyed playing priest because they don't have an interesting card, this card, however, is "extraordinary".
Unstable Element Because rogue is my favorite class.
Dr.Boom Because he will like be the most fun card in the entire set.
Rotspring Because I love the art and want to try it out.
Honorable mentions. The Boomship, It looks like fun but I question the viability of Big Warrior and I don't really want to craft the necessary legendaries to make it work. I also want Whizbang because he is the perfect chill and play casual Hearthstone card. He is almost like a Tavern Brawl in himself and you will likely que into him a lot in casual anyways. Sounds like lots of fun.
Probably only Myra Rotspring for now, because I main rogue. The other cards look cool, but if I can't afford to make a deck from them I really won't bother crafting. Ok maybe [card]Whizbang the Wonderful[/card], because it would help with some quests.