Perian

Perian is a free and open source QuickTime plugin that allows QuickTime to play almost all the video formats. Installation is simple and smooth, after a reload, you will find that QuickTime is able to read all your video files, including the FLV downloaded from youtube !

Put away your MPlayerOSX or VLC, now you can sit back confortablely in your sofa having the small white remote control in your hand, enjoy your videos with Front Row.