i'll admitt, i dont know any yandere from any animemanga that i did watch/read... but i will do something about it. However, i am a fan of seryu ubiquitous from akame ga kill! she was sooo cooooool, i should watch it fullt though...
from video games and vn's: I was a huge fan of yandere simulation before i knew yandev is a lazy son of a bitch, it breaks my heart that he still hasn't finished his game... i also like toko, syo and mikan from the danganronpa franchise, i dunno if they really count as yanderes or yangires, but i see many people call them as such. sadly, i barely remember anything about the story other than the characters death order.
cd dramas...? i never got into cd dramas during my childhood nor in my teens, but now i want to hear more! they're like fun rides and they're much better with yanderes! i tried to listen Yandere heaven, but sadly i could not find a playlist where they translate all the tracks, so later on i'll find a blog post where they have all of them translated into english. I'm also familiar with yandere no onna no ko, i did hear the one with Nagisa but i forgot what happened on that track...
if has to pick a favorite yandere, i guess i would pick... mayu from vocaloid! she is sooo adorable! i'm very glad that we have an official yandere vocaloid! her voice is very soft and sweet for a cute and deadly girl, altough my favorite song from her doesn't have any lovesick lyrics.