VLC is a free and open source cross-platform multimedia player and framework that plays most multimedia files as well as DVDs, Audio CDs, VCDs, and various streaming protocols.
Simple, fast and powerful media player.
Plays everything: Files, Discs, Webcams, Devices and Streams.
Plays most codecs with no codec packs needed:
MPEG-2, DivX, H.264, MKV, WebM, WMV, MP3...