Fun fact: the only other medium I use, apart from pencils is a milky pen! Sometimes this just does the trick, especially with certain finishing touches.
In the photo you can see the light streaks on the head of the bird which I used a milky pen for. I generally do this right at the end to add in those streaks of white which can really make the feathers in a bird or fur on an animal come to life!
It is also very useful to add in that vital white dot of light in the eye. I always say that that dot of light in the eye is the most important part of any animal / bird drawing and again, makes it come to life!