Currently on sale for the grand price of nothing is third-person shooter, EPOCH.2.
The game has you trekking across a post-apocalyptic landscape as you battle robot against robot. Using an intuitive finger swiping control method you'll be able to select targets, dodge incoming fire, make split-second tactical decisions, take cover, and launch various special abilities. Wave upon wave of enemy robots are against you in arena-style combat, so it should be a pretty frantic but satisfying affair.
EPOCH.2 is on sale in honor of it being Apple's pick for App of the Week this week, so expect it to be a pretty limited offer.