VideoLAN

Product: VideoLAN 0.8.6
Company: VideoLAN
Website: http://www.videolan.org/
Type: Free

VLC (initially VideoLAN Client) is a highly portable multimedia player for various audio and video formats (MPEG-1, MPEG-2, MPEG-4, DivX, mp3, ogg, ...) as well as DVDs, VCDs, and various streaming protocols. It can also be used as a server to stream in unicast or multicast in IPv4 or IPv6 on a high-bandwidth network.

In other words, VLC is an universal video media player that will play almost every video file type in existence.