Your choice of ink-drawing pen will depend upon your style of drawing and personal taste. Marker pens with lightfast ink are available in various diameter nibs, as well as brush-style tips. If you use a fountain pen or drafting pen, choose ink made for those pens, as they clog with indian ink. Some artists even use the common Bic biro, though you need to scan these drawings for a permanent record, as the ink is not permanent. My favorite is the old-fashioned split-nib dip pen and Indian ink. The 'buy direct' links are affiliate links to Blick Art Materials.
1. Speedball Standard Point Dip Pen and Nibs
Cheap plastic pen nib holders are available in most art stores and stationers. Nibs come in various sizes, types and strengths: a fairly firm steel split nib is good for all-round drawing. Wide calligraphy nibs are not really suitable - choose one designed for drawing. A copperplate writing nib is softer than a steel nib, and allows you to create a more varied line. Try a variety from your art store to see what you like - they are quite inexpensive.
2. Speedball Standard Pen Holders
Pen holders are so cheap to buy, it's a good idea to grab a few so that you can have one for each nib. I've been known to duct-tape nibs to old bic pen barrels or even pencils at times. These pen holders are a only plastic, but they are a reasonably heavy weight and strong. They have a sort of circular slot carved into the working end which allows you to fit a variety of nib sizes into the holder. I've found that nibs are usually wedged in easily but surprisingly securely. An inexpensive and functional piece of kit.
3. Zig Memory System Writers
I use basic Uniball pens for writing, so I've ended up using them for a lot of sketches too, especially in my journal. They're great. However, they aren't archival, so its worth paying a tiny bit extra for archival pigment ink, especially if you've paid the dollars for the archival paper. Zig claim to be lightfast, waterproof, fadeproof and non-bleeding. We originally bought some for use in photo scrapbooking, but it wasn't long before they found their way into my creative art supplies! If you enjoy working with felt-tip markers and pens, you'll love these.
4. Yasutomo Bamboo Reed Pens
Bamboo pens are rather odd to draw with. They give a rather broad line and don't hold a great deal of ink. The most interesting point was the gradual depletion of ink allowing time for some interesting dryer textural marks, rather like a dry fiber-tip pen. Worth trying when you need something different.
5. Faber-Castell Pitt Artist's Pens
Fiber tip markers don't form part of my drawing kit. My teenager has 'borrowed' them! They are a great way to get beautiful, crisp line and color quickly. These marker pens from Faber-Castell come in a range of nib sizes, and a clever variety of traditional and brush tips (try them to see which suits your style of working). They are lightfast, ph-neutral india and colored inks. They come in black, shades of gray, sepia and a big range of colors. The manufacturers would like to claim that they replace the dip pen (they don't) but are certainly a convenient, affordable addition to your kit. I particularly like the mini packs of 'Manga' colors and the 'landscape' brush pens. Great for gifts and travel.
6. Rotring Rapidograph Technical Pens
Technical pens used to be notoriously difficult to maintain, but Rotring have developed a sophisticated construction that gives a consistent, clog-free ink flow. The cartridges can get a bit expensive if you use a lot of ink, but it's worth it if you love the line. Although some find the line too 'clinical', for some styles of drawing, the crisp, reliable precision of a good drafting pen is perfect and beautiful.