I have a personal browser extension that I use as a grab bag of assorted tools and fixes for sites that annoy me. It's half way between a userscript, a bookmarklet directory, and a UNIX shell, with little commands that run automatically on certain sites or operate on the DOM, and can pipe output to other commands. Here's a very old video of it in action: https://vimeo.com/118090094 (It's no longer open source because I don't want to have to maintain it for other people.)