Continuing with the facial-features theme... noses. Noses are tricky. I know a there's a lot of shortcuts and simplifications out there to draw noses, but I always end up falling back on the anatomy. When you know the shapes of the bits of cartilage, it's easier to play with shapes and sizes and still get fairly accurate noses in fairly difficult positions.
I hope this gives people a different perspective on noses. They really are quite fascinating.