Steamworld Dig was well worth the money. I'd pick it up if I were you. Took me about 9 hours to beat and that is almost 100%ing it. Great fun. I think a second playthrough would be well worth the trouble too.

hmm.. As far as taking turns, not really, but Dear Esther and The Walking Dead were both fantastic pieces that I played through with my girlfriend. Very narrative based though, just good story-telling devices. Gameplay though? If you haven't already, pass the mouse back and forth through Peggle, and Peggle Nights. Amazing for how simplistic they may seem.

Having fun with all the deals? WOO!