Great Downloader easy to use can convert into multiple file formats. Fast and impressive
YTMP3.co.com - YTMP3.co.com is a 100% free multi-format audio and video downloader that lets you convert video and audio from most social media platforms. No annoying ads.
Video DownloadHelper - Browser extension to download videos from the Web
Youtube Video and Audio Downloader - Download YouTube videos in all available formats and extract the original audio files.
youtube-dl-gui - A cross platform front-end GUI of the popular youtube-dl written in wxPython.
y2mate - Y2mate.
y2mate.tv - Y2Mate YouTube Converter is not just a video converter, but also an audio converter. You can easily convert YouTube videos to the format you want, such as MP4 (320p, 480p, 720, HD 1080p), 320kbps MP3, M4A, WEBM, etc.