Not GP, but I'm currently using Vimium under Firefox. I've also heard of Vimperator and Tridactyl but never tried them.

If you're willing to ditch the mainstream browsers, there's Nyxt. For browsing static wikis from a tty, there's ELinks.

I use Qutebrowser which works well and is configurable, though there's no extensions which can be a bit of a bummer, but there's a built in adblocker which works pretty well at least.

Worth noting there is no need for an extension. This comment is also submitted entirely using the keyboard. Tab navigates to the "reply" button.

This. Windows is almost entirely usable with the keyboard, including the file explorer.