NewPipe - NewPipe is a lightweight YouTube front-end for Android.
VLC Media Player - VLC is a free and open source cross-platform multimedia player and framework.
YouTube Vanced - Vanced is a modded version of YouTube with many features such as adblocking and background playback
Minitube - Minitube is a YouTube desktop application.
FreeTube - FreeTube is an open source desktop YouTube player built with privacy in mind.
foobar2000 - An advanced freeware audio player for the Windows platform.