Ace Stream
Ace Stream is a peer-to-peer multimedia streaming protocol, built using BitTorrent technology
FreeTube
FreeTube is a free and open source, multi-platform, privacy-focused YouTube desktop client
MoonPlayer
MoonPlayer is a free and open source video player for playing and downloading online videos from YouTube, Youku, and iQiyi, as well as local videos
SMTube
SMTube is a free and open source program for searching and watching YouTube videos
LosslessCut
LosslessCut – free and open source, simple and ultra fast cross platform tool for lossless trimming/cutting of video and audio files
Shutter Encoder
Shutter Encoder is a free and open source video converter, image and audio handles tool
Musictube
Musictube is a free and open source program to listen to music/songs from YouTube
MPlayer
MPlayer – free and open source, cross-platform media player
QMPlay2
QMPlay2 – free and open source, multiplatform video and audio player which can play most formats and codecs
Celluloid
Celluloid – free and open source, simple media player that can play virtually all video and audio formats, GTK+ frontend for mpv