Macadamia Apps has StillShot (iTunes Link) for the iPhone and iPod Touch in the iTunes App Store for FREE (regularly $1.99)for a limited time.

StillShot can be found useful when objects are on the move and it is hard to catch the moment or when a video was already taken instead of a still photo.

With StillShot users can create a full resolution photo from video files by loading the video and analyzing the frames one by one, letting the user to choose the best frame. The app can extract frames from any video, with no special requirements. StillShot holds the original resolution of the video, e.g., on iPhone 4s the resolution is 1080p (1920*1080px).