UltraStar Deluxe - A free and open source karaoke game inspired by the Singstar™ game, runs on Windows, Linux and macOS.
VLC Media Player - VLC is a free and open source cross-platform multimedia player and framework.
Yokee - Karaoke to YouTube videos
foobar2000 - An advanced freeware audio player for the Windows platform.
KaraFun - KaraFun is the best online karaoke. Over 35,000 karaoke songs, with studio quality, at home or on the go. Regular updates. Free demo!
Winamp - Winamp is a media player that allows users to play multiple-file formats, arrange media in a varied file-management system, and play unique media with AAC encoding.