I've noticed something odd about the font-locking in Emacs Lisp and Lisp mode - keyword args are highlighted using the font-lock-builtin-face and constructs like &optional are highlighted using font-lock-type-face. 

I guess this was was done way back and hasn't been updated in a while, but I think it might a good idea to revise this. Pretty sure those font faces are intended for different usage. I think it would be great if all Emacs programming modes used the faces consistently, so that the meaning of certain faces doesn't change from mode to mode.

I guess that the two modes might also start using the font-lock-built-in face to highlight their core functions (like car, cdr, mapcar, mapc, etc) - as Clojure mode does.