Jumping to the most recent buffer.

gistfile1.txt

(defalias 'last-buffer 'mode-line-other-buffer)

(global-set-key (kbd "M-O") 'last-buffer)

(defun my/split-window()
  "Split the window to see the most recent buffer in the other window.
Call a second time to restore the original window configuration."
  (interactive)
  (if (eq last-command 'my/split-window)
      (progn
        (jump-to-register :my/split-window)
        (setq this-command 'my/unsplit-window))
    (window-configuration-to-register :my/split-window)
    (delete-other-windows)
    (split-window-below)
    (switch-to-buffer-other-window (other-buffer))))

(global-set-key (kbd "M-9") 'my/split-window)