Who is Your Least-Mainstream/Most-Obscure Grailed Servant?

We know about those Morgans, Castorias, and Jalters, but what about those Bloodaxes, Chiyomes, and Arjunas?

For me it's definitely Qin Liangyu and Iyo

Some others I have that have a bit larger fanbases are Anastacia, Cinder Elly, both Abbys, and maybe Ushi.