Here's one I wrote a while ago using the fairly standard technique
of having some data that looks pretty much like the code that uses
the data to reconstruct the data and the code.
;;; Self-reproducing function
(defun v ()
(let ((m '(subst m
'**
'(defun v () (let ((m '**)) **)))))
(subst m
'**
'(defun v () (let ((m '**)) **)))))
-- Jeff