Bookmarklet
Don't even get me started with bookmarklets! It's the most incredible piece of boring technology I can think of!
Some bookmarklets I use
Extract the feed of a page
javascript:void(alert([...document.querySelectorAll('link[rel=alternate]')].filter(e => e.type === "application/atom+xml" || e.type === "application/rss+xml").map(e => e.href)))