One thing that occurs frequently in my Emacs usage is opening a Dired buffer based on the current context of the file I am in. For example, when editing this file I would like C-x d to a Dired buffer representing ~/.emacs.d, and ensure that the buffer represents the current state of the filesystem. The default is for C-x d to require confirmation of the location, and to not refresh the Dired buffer if it already exists. 

(defun mak::dired-here ()
  "Make an up-to-date Dired buffer for the current location."
  (interactive)
  (dired ".")
  (revert-buffer))

(global-set-key (kbd "C-x d") 'mak::dired-here)

While this is a minor change, it is satisfying.