VLC Media Player - VLC is a free and open source cross-platform multimedia player and framework.
TabFloater - Browser extension to use picture-in-picture with any website
foobar2000 - An advanced freeware audio player for the Windows platform.
reEmbed - Custom YouTube Video Player
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.
Vid Repeat - Loop YouTube videos for X minutes or for X times. Loop a full video, or only a selected part, add a delay between the loops, and share the loop with your friends.