FLVPlay HD is a free player based on Adobe Air application which can play FLV format videos. The advantage of using FLVPlay is that it can play both online and offline videos, this means you can either select the FLV video from your PC or enter the YouTube URL of the video and it can stream it for you. It also has a full screen mode and the clarity of videos is also good.
Another good feature is that you can even search videos in YouTube based on keywords or user logins and play it directly from the player interface. The main goal of FLVPlay HD is to provide the user one central place for all his videos regardless the location of the asset. The user has the ability to organize the videos by using playlists, and an hierarchical tree of favorite clips. The application stores the list of recently played videos. This player supports videos encoded with the H.264 high definition codec.
This a good application if you are watching lot of YouTube stuff. This freeware also has full screen mode for watching movies. You need to have Adobe AIR run time to install this application.