This is maybe the slimmest pen available on the market. The winner of an iF product design award this year, and designed by Bobino, the pen not only is very slim, but also comes with an adhesive dock for the inside of your notebook.
You only need to fix the dock to the notebook and slide the pen over it before closing the notebook. This way the pen is protected and always handy for when you need to take new notes.
Bobino designed the Slim Pen in several rich colors, like red, green, blue, white and black, as an ergonomic writing tool. The price is of $5 at Bobino.