If you haven't heard of Machinarium, you probably aren't much of a PC gamer. That's not mean to be some kind of "high and mighty" insult - it's just the truth. Machinarium is a small indie game that was released for PCs and Macs back in September of 2009, developed by Czech studio Amanita Design. It won numerous awards as indie game of the year, as well as accolades for its astounding artwork and soundtrack.
It's a game I think almost anyone can play and love (and hate, but that comes with the territory), which is saying a lot for a click-and-explore puzzle title.