I daydream sometimes about having a browser where tabs behave more like buffers in vim or emacs - that is, with no tab bar or particular ordering on open pages, but with them just hidden in the background, with some kind of about:pages interface (like emacs ibuffer-mode) where I could sort/filter them and bring individual ones back to the foreground.
(Split panel view would be nice, while we're at it.)
(Split panel view would be nice, while we're at it.)