Pen & Ink
Even when I’m just sketching ideas or when I’m drafting illustrations on paper, I now use a drawing pen with detachable nib and drawing ink, and it’s even better for actual paper illustrations that I sometimes create before scanning to a digital format and reworking on computer. This is a relatively new thing in that I used to use graphic art pens and rollerballs before. Really though, Japan is the place to buy this kind of drawing equipment.
Japan is a country of illustrators (think manga-ka), and so there’s some great products. I’m using a Tachikawa T-25 pen with various sizes of nib from Drapas’s Risa range, with Pilot Ink (all of which are made in Japan). They’re comfortable to draw with, give a great result and they’re just a nice thing in general. It’s good to sit down with some green tea and bust out some kanji with it too! But most of all, refreshing to do something away from the glare of a computer screen.