If you've played Card Hunter, you already know that it's great. If you haven't? Here's our review, and here's why we named it Most Original Game of 2013. Also, it's free.
The turn-based card-'em-up has been plucked from the browser and plopped into Steam—hopefully placing it in front of many new eyes. With it comes a new expansion, called Expedition to the Sky Citadel. It's a System Shock-inspired campaign with a Shodan-a-like computerised GM. System Shock and cards might not be a good fit, you may think, but Blue Manchu founder Jonathan Chey just happens to have co-founded Irrational.
The campaign now also supports co-op—letting two or three people collaborate against the demon and/or cyberpunk hordes.
I mentioned it's free, right? You should head here to give it a go.