Mac OS X only: If you're tired of QuickTime X's minimal approach to features or VLC's clunky, not-so-pretty interface, free app MPlayerX brings a smooth, easy-to-use player to OS X with support for multiple video formats.MPlayerX is like the awesome love child of VLC and QuickTime X—an intuitive, good-looking UI with a bunch of extra preferences, as well as support for any video format under the sun. Not only can it play everything you throw at it, but you can control it with multitouch gestures on your trackpad, control it with the Apple Remote, stream video from the web, and remember your play position every time you start it up. It can even automatically detect when you're watching a TV show with multiple episodes in the same folder, and continue on to the next episode on the list with just a keystroke (and that's just scratching the surface of its features). Don't get us wrong, we love VLC, and it is still super powerful, but its interface isn't exactly the most friendly. If you don't use VLC's super advanced features and you want something a bit easier to use, try MPlayerX—it's the video player to beat on the Mac.
MPlayerX is a free download for Mac OS X only. You can download it from its home page below, or head straight to the Mac App Store to check it out.