i can also recommend the Micron 08 pigma pen, made by sakura color products corp. mine says "#1 archival ink". i think i got it at jhittle.com
i'm sure there are plenty of good ones on the market. this is the first of those i've tried that makes a nice sharp line.
i'm a dharma fan so was happy to see the recommendation of their pens. i've been wondering if they'd work well. item added to shopping list. :-)