Great Downloader easy to use can convert into multiple file formats. Fast and impressive
FFmpeg - Open source multimedia suite for conversion, playback, profiling, and streaming.
Video DownloadHelper - Browser extension to download videos from the Web
HandBrake - HandBrake allows users to easily convert video files into a wide variety of different formats.
youtube-dl-gui - A cross platform front-end GUI of the popular youtube-dl written in wxPython.
Adobe Media Encoder CC - Create optimized video for any screen size and resolution with Adobe Media Encoder. Available only in Adobe Creative Cloud.
Youtube Video and Audio Downloader - Download YouTube videos in all available formats and extract the original audio files.