I can't choose so I'll list few:
HAYAKAWA NOJIKO - her art is just too beautiful, but sadly so many of her manga are forever unfinished, at least here... But Endou-kun no Kansetsu Nikki and Kurayami ni Strobe are, and they are fucking beautiful.
HIDEYOSHICO - idk what is it about her work, but it has this charm that just has me going back to it all the time -Udagawachou de Mattete yo, Stay Gold
TAGURA TOHRU - I've never been as emotionaly invested in BL as with his(?) manga. Koimonogatari, NomixShiba
NISHIOKA KYUOIDAI - their work is very abstract, could be described as horror ig, art is very simplistic but I love it, and when I read their manga it somehow feels like it's lifechanging idk - Kono Yo no Owari ni e no Tabi, Kami no Kodomo
Drop me your FAVOURITE MANGA AUTHOR!
Specially those that makes a lot of good manga. I'll go first, Yamamoto Kotetsuko, author of Honto Yajuu, Mad Cinderella, and many more.