youtube-dl - A small command-line program to download videos.
youtube-dl-gui - A cross platform front-end GUI of the popular youtube-dl written in wxPython.
4k Video Downloader - 4K Video Downloader is a software program that helps people download video files from sites such as Facebook, YouTube and Dailymotion.
Video DownloadHelper - DownloadHelper is a tool for web content extraction.
Freemake Video Downloader - Freemake Video Downloader downloads videos from more than 10,000 sites. Absolutely FREE. Download YouTube in HD, MP4, MP3. **Voted best of 2018**.
ClipGrab - A friendly downloader for YouTube and other sites