David (Steam key/Region free).

http://store.steampowered.com/app/346180/David/
Summary
David is a game. A game about physics and enemies. A game about struggles and life. A game about David.

This game is designed to be difficult. I poured myself into developing this game for nights and nights and nights. It´s almost tough to share. I hope it feels strangely personal.
Description
You play David, an awfully small abstracted chosen hero tossed into a blissfully simple world overrun by giant culminations of evil physics-beasts. As David, you are given a slingshot-esque gift that you will have to use to conquer your colossus foes. Hold, aim, and fling to attack (Angry Birds™ style!).
Features
a 9-level Campaign, 3 Additional Levels, a Survival/Arena/RPG mode, a Secret Basket-ball-pit Minigame, and hats!