Alien Blue (iPhone, iPad and iPod touch)
One of the best Reddit clients I've used on any platform, Alien Blue provides all of the features avid Redditors need in a clean, simple and intuitive interface. And it's also free. Other Reddit apps are available for a variety of mobile platforms, but Alien Blue is one of my favorites. A $1.99 "pro" upgrade unlocks advanced features, including comment-link previews and "Retina" thumbnails (for devices with Retina displays), among other things—but the free version is packed with everything you need to embrace Reddit on the go.