Anime girl who pretends to be a boy/looks like a boy/dresses in a suit or gender neutral clothes?

haruhi from ouran high school host club

Souseiseki from Rozen Maiden happens to be quite masculine, despite being female.

She even often refers to herself using male pronouns instead of female or gender-neutral like most of the other characters.

This beautiful waifu here! Saber!!!!!!! She looks super cool in a suit. Liove dem gender neutral clothes! Fate series btrw

If your looking for actual transgender characters you can try link

integra hellsing is wearing a suit pretty much the whole time...but idk if that´s what you were meaning..

Masumi Sera from Detective Conan. Everyone mistaken she is a "HE" when they first met her as she always boys clothes and has a petite figure. She is tomboyish too. She also use male pronouns. :3

Leah from Le Chevalier D'eon often wears her brother's clothes.

Amane Ohtori from "Strawberry Panic".

Kiyone Kotetsu (Bleach)

Two of the paper sisters in Read or Die TV could be mistaken for boys. Maggie (left) and Anita (center).

Hi :) Sorry for the lack of images but I highly recommend you check these out! Have a nice day :)
Kurau Amami - Kurau Phantom Memory
Kino - Kino's Journey
Emma - The Promised Neverland
Evie - The 100st Heroine
Makoto - The Girl Who Leapt Through Time
Tachibana - Aoharu x Machinegun
Anna - When Marnie was there