Cog is a powerful tool for playing various audio files. It comes with support for a great deal of audio file formats: Ogg, Mp3, Flac, Monkeys Audio, ACC, and it also supports playing audio files from different video games.
It has a simple interface and an easy-to-use menu. The preference menu only allows users to make changes upon the hot-keys used, the directory where the audio files are located in, remote access, output settings and LastFM (a well known music-related application) support. It does not provide any customizing settings for the overall use of the tool, or for setting up the appearance. In my testing, the application stopped working several times and some times it seemed to play the files, but with no output sound, so I find this version to be buggy and quite unreliable. The main window provides details about both the file playing and the playlist loaded, and an extra window named Info Drawer will provide you with more advanced details like bitrate, frequency, channels and Bps.
All taken into consideration, Cog is a small player for audio files and comes with high support on audio file extensions; however, the current version appears to be buggy and unstable, so it requires further development.