Here are the top 25 inks listed by popularity from the Fountain Pen Companion website. That site continues to list many more inks down to those submitted by only one user. The number in parenthesis is the number of users with that ink in their collection. On the Fountain Pen Companion website you can click on an ink's name to see swatches of the color and user reviews. Nice!
Diamine Oxblood (882)
J. Herbin 1670 Emerald of Chivor (873)
Pilot Iroshizuku Yama-Budo (831)
Diamine Ancient Copper (815)
Pilot Iroshizuku Kon-Peki (810)
Diamine Earl Grey (638)
Noodler's Apache Sunset (631)
Robert Oster Fire and Ice (579)
Diamine Aurora Borealis (549)
Rohrer & Klingner Alt-Goldgrün (534)
Pilot Iroshizuku Shin-kai (534)
Pilot Iroshizuku Tsuki-yo (518)
Pilot Iroshizuku Asa-Gao (511)
Organics Studio Nitrogen Royal Blue (510)
Waterman Serenity Blue (497)
Diamine Red Dragon (490)
Pilot Iroshizuku Ku-jaku (485)
Noodler's Black Swan in Australian Roses (469)
Sailor Shikiori Yama-Dori (465)
Pilot Iroshizuku Murasaki-Shikibu (463)
Pilot Iroshizuku Syo-ro (440)
Diamine Autumn Oak (428)
Diamine Sherwood Green (427)
Pilot Iroshizuku Fuyu-Gaki (421)
Sailor Manyo Haha (421)