In my old project there used to be many #if 0 .. #endif which does not fall in to the comment-face of the c-mode. This always confuses me. It would be good if that block is colored like a comment. So that i can just ignore that place.
I wrote the following elisp code which adds the #if 0 section to the comment section keywords of the c-mode.
'(("\s-*#\s-*if\s-*0\s-*n\(.*n\)*?\s-*#\s-*endif\s-*" 0 font-lock-comment-face append)))
I have left \s-* in many places as it is because even using back reference does not improve any readability.