Huh, Joe Chill eh? wasn't expecting that.

Sorry, late post. Missed a line of "Cold Case.

The Heroic Spirit is Joe Chill.

John Wilkes Booth?

Anyway, this is pretty interesting. Mind if I give some suggestions?
Miki Sayaka, from Puella Magi Madoka Magica. She'd work well as Shirou's Saber with their shared justice obsession, as Illya's Berserker (enraged over the perceived abandonment by Shirou and Kiritsugu), or as Kiritsugu's Saber (for hating Kiri, like Artoria did but worse)

Junkrat, from Overwatch: He'd do good as... well, any Berserker, really.

Ayanami Rei, from Evangelion: I was thinking that she'd be Sakura's Rider. NGE or Rebuild, I think either would work. Some fairly disturbing parallels between them.

Tsukishima Shukuro, from Bleach: Makes for a pretty terrifying True Assassin.

Matoi Ryuko, from Kill la Kill: She works as a Saber or Berserker (possibly Rider). Satsuki would work just as well (although Assassin instead of Berserker). Ryuko might work as Sakura's Grail-corrupted Saber.

Malori Crowett, from Mage & Demon Queen. Obviously a Caster, and equally obviously that her NP would have to be Velverossa.

Illyasviel von Einzbern, from Fate/Kaleid Liner Prisma Illya: If she's summoned with a Class Card installed, she could be of any class. I was particularly thinking of being either Kiritsugu's Saber, Shirou's Saber, or Illya's Berserker, though.

Wreck-It Ralph: Berserker. Probably work best as Illya's.

Flowey the Flower, from Undertale: Berserker (Kariya or Illya, manipulating either would work) or Avenger. Possibly as Assassin or Caster (he'd probably get along with Ryuunosuke).

Hornet, from Hollow Knight: A viable Saber, Lancer (if you think of her needle as long enough and considering how she pretty much exclusively stabs you), Archer, or Assassin.

Curly Brace, from Cave Story: Archer (or Rider for comedic value). Probably better for Rin... I can't see anything particularly interesting being born out of being summoned by Tokiomi.

Centorea Shianus, from Daily Life with Monstergirls: Saber (or possibly Rider, depending on your interpretation of whether a centaur can be considered to be riding herself). Either option would give some interesting interactions, regardless of which Holy Grail War you use.

Nia Teppelin, from Tengen Toppa Gurren Lagann: I was thinking of MoonCancer, actually.

Helltaker, from Helltaker: Berserker (or Rider, in the same sense as why Medb's a Rider). Probably be a pretty funny chapter.

Duck, from Princess Tutu: Caster, most definitely. Princess Tutu needs more love.

Sarah Kerrigan, from StarCraft: Depending on which point in time she's summoned from, anything from Archer, Lancer, Caster, Rider, Assassin, Berserker, or Avenger fits just fine. Lot's of room to work, there.

What?
The Grail is corrupted because it absorbed Angra Mainyu. Why would it summon anything but All the Evils of the World?
Assassin would have been more appropriate-or perhaps Rider or Archer.

If we are being honest alucard wouldn't win against Gilgamesh...

So I just read chapter 33 and I noticed all but one of the ‘servants’ are not servants the one servant in the stories is Sherlock Holmes he is a ruler class servant in fate/grand order... now that I’m reading this this came out in 2013 and fate/grand order was 2016 ignore everything I said

Batman?

gonna guess it's the guy who killed batmans parents

do solo leveling mc

clue- origin of a dc character

Perhaps you could do Ghost Rider (Berserker) or Kain (Saber)

Accelerator from A Certain Magical Index Season 3 as Berserker. His black wings usually comes out when he loses his mind, after all.

My suggestion, Future Trunks from DBZ, I want that so bad.

You make all of them. A bunch of op even if some of them like aragorn that is simply impossible

I loved this just as much the second time as I did the first. Such a great Constantine story, even at only two chapters.