UltraStar Deluxe - A free and open source karaoke game inspired by the Singstar™ game, runs on Windows, Linux and macOS.
GSnap - With GSnap you can get an auto-tune effect.
Yokee - Karaoke to YouTube videos
Revoice Pro - Revoice Pro is an audio plugin used for vocal tuning, time correction and ADR.
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!
CrispyTuner - Fully featured vocal tuning suite.