My go-to fine-liners, as someone who sketches/inks, are the Sakura Pigma Micron pens. They used to be much harder to find but nowadays I see them all over, in most art supply shops, they're pretty popular.
Plus they're pigment based, so the ink is durable and long lasting. I actually have a few for some that I'd like to last a long time. However, I'm not a huge fan of how they fell. It's like writing with a marker.
I understand gel ink pens are pigment based too, but archival stability doesn't seem to be as much of a selling point for them, so I don't know if they're as suitable/stable. I tend to use them for day to day stuff.
I recently got some technical pens - basically refillable fineliners - by Staedtler, actually - and am enjoying those though.
They are widely available at most office supply stores, too, in the drafting/drawing aisle.