One of my favorite movies of all time is "Aliens" (not to be mistaken for it's predecessor, "Alien"). It is actually a lot of fun drawing the gross, skeletal anatomy of a Xenomorph alien from the movie.
The main thing about this picture is that I am trying to practice good consistent lighting on the Xenomorph's shiny black exoskeleton by crosshatching the heck out of the figure. My normal intuition is to just black out the Xenomorph's skin with a flat black marker and draw some squiggly lines to imply shininess. Normally, that is a pain the butt for me to crosshatch that much, but the end result is that it makes the figure pop out and look much more realistic.