I stumbled on a C'Thun Control Shaman list at /r/competitivehs and started tinkering with it. I was little skeptical at first, but I ended up with a seemingly viable decklist.
It seems favorable vs DH and Hunters (at least the aggro variant) and somewhat surprisingly, against ETC Warrior too thanks to C'Thun burst. It's basically a Galakrond stall Shaman with C'Thun added into it. I also added Polkelt & Lady Vashj for added draw and contingency (for tutoring out assembled C'Thun, shuffled Vashj Prime or just Galakrond). Polkelt is probably optional here, but so far it feels like a good addition.
I recently swapped in Serpentshrine Portals in favor of Walking Fountains, as they seemed tad too slow and often clogged my hand. There's probably room for improvement, but it's been working reliably vs aggro & Evolve Shaman.
One thing I can think of is that if you play Polkelt before Lady Vashj then she becomes kind of hard to play as she will re-shuffle your deck...otherwise interesting deck, maybe double Witch's Brew is a bit too much also? Perhaps some Far Sight for extra draw could be good, especially given the small number of low cost cards, you should almost always get full discount value...
I tried out swapping Polkelt for Far Sight and it seems to work alright as well. The idea of drawing into 0 mana Far Sight is...tempting, to say the least :) Double Brews are for redundancy, the Diligent + Brew combo is often enough to make aggro concede (unless they've got massive board presense already). Sometimes you just don't have the luxury to wait for both pieces, even in Control matchups you can use it to rapidly heal your minions if self-healing isn't necessary.
Polkelt can get little awkward if you don't draw Mana Tides beforehand so there's that too. Polkelt may not be the ideal choice with Mana Tides, but majority of the list feels quite solid.
Update: Replaced Polkelt with Far Sight due to upcoming nerfs.
Today I hit Diamond 10 at 71% winrate (21 - 6) Paladins being the toughest matchup. Still, this deck has been consistent vs DHs, Hunters (aggro and HL variant) and even against some greedier Control lists (ETC Warrior, Res Priest and Clown Druid with a bit of luck). It can grind out fast aggro decks with AoE's (unless mulligans and early draws are utter shit) and slower matchup attricion wars can be won through Galakrond, C'Thun's BK and/or Diligent + Serpentshrine or Dunk Tank bursts. At the moment I wouldn't swap out a single card, but if Paladins pick up after the next patch I'd toss in another Devolving Missile (and maybe even 1x Earth Shock/Wandmaker/Cobalt for good measure).