VLC Media Player - VLC is a free and open source cross-platform multimedia player and framework.
Nightingale - Nightingale is a free and powerfull music player for Linux, Windows and Mac
MPlayer - MPlayer is a movie player which runs on many systems (see the documentation).
GNOME Music - Music is the new GNOME music playing application.
Windows Media Player - Get information about Windows Media Player and other Windows Media technologies.
Roon (Music Player) - Roon is a music playing application for audiophiles