Sometimes I need to copy the name of the currently visited file to the clipboard. Emacs does not have a built-in command for that, but cooking one is pretty straightforward:

(defun er-copy-file-name-to-clipboard ()
  "Copy the current buffer file name to the clipboard."
  (let ((filename (if (equal major-mode 'dired-mode)
    (when filename
      (kill-new filename)
      (message "Copied buffer file name '%s' to the clipboard." filename))))

Evaluate the new bit of code in Emacs (maybe by using C-M-x somewhere in the body of the function definition) and invoke the command with M-x er-copy-file-name-to-clipboard.