Sometimes it feels like Goat Simulator by Coffee Stain Studios is always coming on sale, but I'm not complaining.
This utterly daft game will make you smile, even if it's in a 'what IS this game?' kind of way. Goat Simulator does mostly what it says in the title - it's a goat simulator, only there's a ton of random things to do. From ragdolling one hundred feet in the air, to licking a human and dragging them along with you, it truly is bizarre.
The original Goat Simulator is currently free on the App Store for a limited time, though none of its other titles have been discounted at all.
Google Play on the other hand may not have any titles for free, but all of the games in the franchise have been discounted to £2.49 for Goat Simulator, and £2.09 each for Waste of Space, GoatZ, and MMO Simulator.
Oh, and just before you go, unless the bugs you encounter break the game, they're supposed to be there. Enjoy your under-the-map diving and disturbing model contortions.