reEmbed - Custom YouTube Video Player
Headset - Personal music player for Youtube and Reddit
TabFloater - Browser extension to use picture-in-picture with any website
Plexamp - A small music player with a number of unique features
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.
Poolsuite™ - The super-summer music player