Great Downloader easy to use can convert into multiple file formats. Fast and impressive
FreeTube - FreeTube is an open source desktop YouTube player built with privacy in mind.
Video DownloadHelper - Browser extension to download videos from the Web
NewPipe - NewPipe is a lightweight YouTube front-end for Android.
youtube-dl-gui - A cross platform front-end GUI of the popular youtube-dl written in wxPython.
Minitube - Minitube is a YouTube desktop application.
Youtube Video and Audio Downloader - Download YouTube videos in all available formats and extract the original audio files.