Blind contour drawing, portrait. (remember how much fun this was)?
Line Drawing: A Guide for Art Students
Cross contour line drawings by Tornwing: black lines of different thicknesses flow around three-dimensional forms. The strong contrast in this drawing creates a striking graphic image.
Cross Contour FUNTIME. by HanMonster.deviantart.com on @DeviantArt
Student example of cross contour drawing from Beginning Drawing - Drawing 1 class of Allan Innman. Art by Sophie Banspach
Kris Trappeniers - ballpoint on paper - continuous line drawing This is one of the coolest continuous line drawings I have ever seen. Instead of looking completely askew it is pretty proportional and has the appropriate shading.