All you need material-wise is pen, paper, and ink. That's it. The initial investment means giving up lunch one day....ten bucks perhaps for a starter. They're small and convenient, good for those infected with wanderlust. They come in many varieties, for all those picky people out there: dip pens, technical pens, markers...and the office pen. All the maintenance involved in a technical pen is merely cleaning it once a month. Dip pens clean up even easier. Easiest of all to clean are the toss-aways.
The variety continues on to surfaces...art board, bristol, paper, mylar, watercolor paper, and others.
With so much convenience put into one handy little tool...it's amazing that the search on deviantART for pen and ink yields only...a...lot...of deviations. hehehe.
Without further ado I present to you: a small sampling of some the amazing pen and ink to be found on DeviantART: