Minitube - Minitube is a YouTube desktop application.
YouView - Browse, watch, convert, and download YouTube videos on your Mac faster, because YouView uses the core technologies of Mac OS X to play instead of Flash allowing video to run smoother on systems with lower specs.
MenuTube - Do you enjoy listening to YouTube's podcasts, audiobooks, interviews or anything else that...
YouTube Media Player - Media Player is an open-source project that aims to enhance the overall YouTube experience.
Tubbler - YouTube Movie Player for Mac OS X.
QadamSoft Player - QadamSoft Player provides a desktop based interface for watching youtube videos.