Audio Playr (was Little Audio) is a handy tool to play and export almost any file that contains audio. It can handle almost anything you throw at it, as long as the file contains audio in some form. Everything from odd audio formats to movie file containers and you can export everything back to AAC or Apple Lossless. Some of the file formats/containers supported are AIF, MP3, FLAC, M4A, M4R, CAF, MOV, MP4, AVI, MKV, WMV, ASF, FLV, MPG and many, many more.
Little Audio App can't read DRM-protected files from the iTunes Store.