GTK YouTube Viewer - A lightweight application for searching and streaming videos from YouTube.
VLC Media Player - VLC is a free and open source cross-platform multimedia player and framework.
FreeTube - FreeTube is an open source desktop YouTube player built with privacy in mind.
AIMP - AIMP : Free Audio Player : Официальный сайт программы
Minitube - Minitube is a YouTube desktop application.
foobar2000 - An advanced freeware audio player for the Windows platform.