(I recognize that what I like isn't for everyone, but these are all fantastic reads in my opinion! I'm not caught up with all of them, but so far I love them all.)
Phantom Tales of the Night
Kiichi!!
Kiichi!! VS (sequel to the previous one)
Mononoke
Kings' Viking
Clover (tetsuhiro Hirakawa)
Totsukuni no Shoujo
One Piece
Gangsta.
Oyasumi Punpun
Jojo's Bizarre Adventure
Pet Shop of Horrors
Death Note
Hunter x Hunter
Monster
To You, The Immortal
Innocent (sakamoto Shinichi)
Vinland Saga
Berserk
Omniscient Reader! It's widely discussed now!
https://www.mangago.me/read-manga/3_ban_sen_no_campanella/ (beautiful and poetic story about a guy who goes through heartbreak and eventually finds love again)
https://www.mangago.me/read-manga/stigma_marloong/ (MC and ML are both traumatized by past events and only show their vulnerable sides to each other. They eventually fall in love.)
https://www.mangago.me/read-manga/get_back/ (Three friends get split up when they get adopted. They eventually reunite.)
https://www.mangago.me/read-manga/savage_garden/ (MC's friend dies in an unfortunate circumstance, and has to take his place in a private academy for the rich. During her stay, she encounters the sick and twisted lives of the rich and falls in love.)
https://www.mangago.me/read-manga/life_senjou_no_bokura/ (Two men fall for each other.)
https://www.mangago.me/read-manga/homeless/ (MC decides to live in his high school dorm after his mother passed away, which is rumored to be haunted. There he meets a guy who he disagrees with 24/7, but having past trauma with the paranormal due to his mother's job as a shaman, he refuses to live in this dorm without another person, leaving his only choice of a roommate to the guy he hates.)
https://www.mangago.me/read-manga/secret_lady/ (In the MC's past life, she was able to see ghosts, and was outlasted because of it. Reborn again into a strange world, the MC also sees ghosts, but decided to keep this a secret in fear of living life like she did previously.)
https://www.mangago.me/read-manga/weak_hero/ (MC moves to a delinquent filled school due to an unfortunate circumstance in his past school. Bullies pick on him because of his weak appearance, but little do they know, he is as ruthless in his fighting methods as well as he is at getting good grades.)
https://www.mangago.me/read-manga/isekai_omotenashi_gohan/ (MC and her sister, along with their house, are transported to another world.)
https://www.mangago.me/read-manga/a_returner_s_magic_should_be_special/ (MC dies and is returned to his past self. He's adamant on saving all of his comrades as well as the world which fell under ruin in his past life due to an evil organization and their creations.)
https://www.mangago.me/read-manga/tondemo_skill_de_isekai_hourou_meshi/ (MC was transported to another world and cooks for a powerful and mysterious creature who only seems weak to the pleasure of good food.)
tokyo ghoul+:re
golden kamuy
shimanami tasogare
there's more but i can't remember
Any manga you think people are completely missing out if they don't read it?