I've been playing a shitload of Blizzards new CCG, Hearthstone. It's in open beta now, and very addictive to any fans of M:TG/Yugioh/Pokemon cards, etc. I'm a semi-serious magic player from way back, and took to hearthstone like a duck to water. Love how much cheaper it is to play than MT:G... in fact it's pretty viable to be a FTP player... unlike most freemium titles in this genre - you can actually get access to all the cards as a free player, buying cards just speeds the process up.
Pick it up if you like collectable card games.