My GRAIL-PEN: The Pelican M215 with rectangles is a kind of grail pen for me. Not because it is such an expensive pen but for a very different reason. As a teacher of mathematics and engineer, I have a lot to do with drawing straight lines, straight angles and geometric figures. If you have to draw a rectangle on a blank sheet of paper, you can do so by drawing the lines longer than necessary to make a proper right angle. You will eventually end up with rectangles as on the Pelikan M215 pen. This M215 series of pelican also includes a variant with rings and with diamonds. Also fun, but less special in my view. Ring and diamond patterns can be found on many more pens. The way the rectangle stands on this pen is really unique. You will not come across any other fountain pen, as far as I know. Therefore: as a technician, math teacher and fan of Pelican pens this is THE grail-pen for me. What is your GRAIL-Pen and why?