GOM Player has many features such as a codec finder, ability to play broken AVI files, multiple media file support, and screen capture which allows you to take video screen shots directly from the player.
The default GUI is straight forward and easy to get you started watching videos or listening to audio.
There are some cool panels to tweak both video and audio.
Of course there are also a variety of skins you can download from their site. For instance here is the example of the XP Metallic skin.
With a plethora of video and audio tweaking options, and a relatively smooth and crisp video playback, GOM Player is definitely worth a look!