If you spend a considerable part of your life watching YouTube videos, you would appreciate me for compiling this list for you. Remember that you will either require Firefox or a browsers that supports userscripts, like Opera and Safari, to use these tools. So here we go.
Removing distractions from YouTube page
Quietube: This is the most recent of all YouTube tools, so let me mention this first. Quietube is a browser bookmarklet that removes all distraction from the YouTube page which includes comments, advertisements and well … everything, except the video. Just drag this bookmarklet to your browser’s bookmark toolbar and whenever you land on a YouTube page, click on the bookmarklet to quickly wipe out everything from the page. Want to share the video with someone? Click on the Tinyurl link at the bottom of the page to automatically create a Tinyurl shortened URL for sharing.
YouTube Comment Snob: YouTube comments are worthless, we know it. But still if you don’t like the idea of removing all comments from YouTube, then you can try this Firefox addon. YouTube Comment Snob allows you to filter out trashy comments based on customizable rules like spelling mistakes, excessive punctuation (!!!! ????), excessive capitalization, profanity and such.
Video Focus is another distraction free tool, this time in a Greasemonkey script format. The script allows you to turn on or off comments, related videos, and also allows you to resize the browser to fit the video, change background color and also download videos. Video Focus supports more than 70 video sites.
Preventing AutoPlay of videos
TubeStop is a Firefox addon that prevents autoplay of YouTube videos. Useful when you open a number of YouTube tabs at the same time intending to view them one after the other. For non Firefox users there is a userscript YouTube Prevent Autoplay. Of course, you can use it with Firefox too.
HQ YouTube videos
YouTube HQ + 720p Ultimate is a Greasemonkey script that automatically switches all YouTube videos to high-quality, if it’s available. It ensures that you always get to view a video in it’s highest available resolution without having to seek for it yourself. This script also comes with the autoplay off feature.