Infinity Blade II is not the freshest game available on the App Store, but when the price drops from $11 to free, can you really complain about its age? Even though it came out late-2011, it still looks amazing and if you have a recent device, it'll run great as well.
If you're not familiar with the series, it's basically a rogue-like with a touch-based, hack-n-slash mechanic. I'll be honest, I found the combat rather frustrating -- all it takes is for a frantic swipe to go undetected to lose a fight during the game's harder moments.
But, if you can get past the sometimes-finicky controls, there's a lot of fun to be had. Again, for the cost of nothing, it's an excellent deal. The developer, Chair Entertainment, has also kept the game up-to-date and it's fully compatible with iOS versions ranging from 6.0 to 10.0.