VLC - Open-source Multimedia Player

VLC (a project of VideoLAN) is a free and open source cross-platform  (It works on Linux, Windows, Mac and iOS! ) multimedia player. It's a player that fulfills all your needs. It handles various audio and video formats, including MPEG-1, MPEG-2, MPEG-4, DivX, MP3, and OGG, as well as for DVDs, VCDs, TV cards, streaming protocols and much more.
It is simple to use, yet very powerful, portable and extendable.
screenshot of VLC, find more here.
Video formats feature of VLC, see the full features here
I can't promise how is the performance of VLC on Mac as I don't have a Mac, but it's definitely a nice media player on Linux and Windows. In addition, VLC is just coming to iOS, so don't require too much on it right now.

Homepage & Downloads