The "Granat" pencil sharpener by Möbius+Ruppert was patented by a Frenchman with the name de Thierry on 14th April 1847, and it has been produced in more or less the same form ever since, earning itself a reputation as a design classic. It weighs a hefty 23g, doesn't mind kicking around in a pencil case or backpack and sharpens your pencils perfectly with its hardened steel blade.  
It's the only sharpener you'll ever need, though you may want to replace the blade every now and then. (Also in our shop.)