I've recently started using fountain pens, the Pilot Capless (Vanishing Point) Decimo with Pilot Iroshizuku Shin-kai ink in particular. The Decimo is retractable, making it great for everyday use. My paper of choice is Rhodia R 90gsm.
It's refreshing to write with something as tactile and manual as a fountain pen when I'm surrounded by screens all day. I find that taking notes on paper helps me with programming (debugging, code structure, etc.), and the writing experience of a fountain pen encourages me to take more notes.