Civilization V on Steam, free of charge.
You can install the game through Steam and play until you bring the world around to your type of thinking, up until 1pm PT on Sunday. And if you like Civilization V, it just so happens you can also purchase it at a 75% discount this weekend, which brings the price down to $7.49. A good ruler must also be able to spot a good bit of marketing. The expansion, Gods and Kings, is a little more than a month away, after all.