Aluminum MUJI Fountain Pen. $16. Purchase.
UPDATE [11.17.2014] While I love the design of this pen, it has not proved to be the most useful. Let me preface by saying that I don’t know enough about fountain pens to write knowledgeably on the subject, but in my experiences the pen dried out rather quickly, not from use, but from the passing of time (evaporation due to no seal?). After replacing the cartridge and cleaning the
head of the pen of the dried ink, it never quite wrote smoothly again. Consequently, I’ve given up on this pen and wouldn’t recommend it. Instead I’d recommend the Parker Jotter, which I’ve been happily using daily for well over a year. They’re different styles of pens and thus not exactly comparable, but if you’re looking for a minimalist EDC pen go with the Jotter.