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.

Features

Simple, fast and powerful media player.

Plays everything: Files, Discs, Webcams, Devices and Streams.

Plays most codecs with no codec packs needed:
MPEG-2, MPEG-4, H.264, MKV, WebM, WMV, MP3...

Runs on all platforms: Windows, Linux, Mac OS X, Unix...

Completely Free, no spyware, no ads and no user tracking.

Can do media conversion and streaming.