KMPlayer is a audio/video player that supports a wide range of file formats, including AVI, MKV, MPEG, OGM, MP4, ASF etc. without any additional codecs installed. It also has full VCD/DVD playback functionality. In addition, it is able to play incomplete/damaged AVI files, or media files that are locked while downloading or sharing.
Note: In the past, this application managed open source components against the terms of their respective licenses. The current status of this is unclear.