I really like Muji pens because of their no-nonsense, minimalist design. The pens themselves are gel pens with a really precise writing tip, so they are good writing instruments on their own. But they are also extremely desirable due to their non-branded, clear plastic casing. You can instantly see which color ink you are using and how much you have left, and the translucent plastic gives the pens a simple yet elegant and not cheap looking aesthetic. I also love how they have their tip point value on the top of the cap so you can easily see which pen you are selecting.