MPlayer was originally ported a while back, and has then been superseded by this version, and is considered the official Mac port by the original developers.
From the official website
MPlayer OSX Extended is the future of MPlayer OSX. Leveraging the power of the MPlayer and FFmpeg open source projects, MPlayer OSX Extended aims to deliver a powerful, functional and no frills video player for OSX.
MPlayer OSX Extended is based on the original MPlayer OSX project but has since undergone fundamental changes, making it a modern and easy to use video player. Thanks to multithreading and 64bit architecture, MPlayer OSX Extended is one of the fastest choices on OSX to play back HD H264 videos. It also supports instant playback of MKV files and advanced styled subtitles in the ASS format.
MPlayer OSX Extended uses the MPlayer open source project for decoding and integrates MPlayer's default key commands with a native OSX interface. Users of MPlayer should immediately feel at home and are able to tweak the fine details of the MPlayer invocation with binary bundles and additional command-line options.