Treasure Hunter is a card game designed by Richard Garfield. If you're not in the know, that's the same guy who designed Magic: The Gathering, as well as a swathe of other incredibly addictive games.
Well, right now Treasure Hunter is on sale on the App Store for just 99p / 99c. That's the cheapest it's been since it came out on iOS a couple of years ago.
The game sees you competing against either an AI or a human opponent to grab the most treasure. It's easy to pick up, but there's a surprising amount of depth here as well.
And for less than a buck, you can't really go wrong. Hit this link right here to go to the App Store and pick up the game while it's cheap.