The iTunes App Store offers downloads of Sentinel 3: Homeworld for iPhone and iPad (pictured) for free. That's a $3 drop, $1 below out September mention, and the best price we've seen for this sci-fi tower defense game.

Of note: The iTunes App Store also offers downloads of Pro Tuner for iPhone and iPad for free. That's $4 off and the best price we could find for this chromatic tuner app designed for guitar and bass.