Firefox address bar
The killer feature is that you can extend this with your own macros. E.g. if you want the address bar to recognize "hn " as a prefix keyword, and redirect "hn firefox address bar" to, say, Algolia — you simply create a bookmark with "Keyword": "hn" and "URL": "<a href="https://hn.algolia.com/?q=%s" rel="nofollow noreferrer">https://hn.algolia.com/?q=%s</a>" (not actually a URL, don't click on it) – %s indicating where the macro parameter substitutes. Then "hn firefox address bar" macroexpands to<p><a href="https://hn.algolia.com/?q=firefox%20address%20bar" rel="nofollow noreferrer">https://hn.algolia.com/?q=firefox%20address%20bar</a>