Unlike Shiny, I have a hard on for Monk-ish characters so they were usually in my main 3/4. :x

FFVI - Relm, Umaro, Gogo, Strago
FFVII - Cait Sith, Yuffie, Red XIII
FFVIII - Quistis, Selphie
FFIX - Quina, Eiko
FFX - None really. I guess I use Lulu the least though.
FFXII - Penelo, Fran
FFXIII - Didn't play enough of it.

I apparently am not a fan of Blue Mages though.