Yandere Kanojo should have an anime even it will be as short as chitose get you & chibi devi!.
The series is somewhat similar to yankee-kun to megane-chan but shorter by release since its more on 4-koma style.
Even though it's a mahnwa, I think it would be nice if Tower of God got animated. The webtoon resembles a storyboard for an anime/cartoon already so I'm sure it won't be too difficult to adapt on screen.
I think the action scenes would look brilliant in motion.
I would want The Flow Stream to get one (probably my favorite, school and being able to use magical abilities)) and Soul Cartel (action would look great for Mephistos attacks)
Cowboy bebop is anime series, lately adapted to manga. I love its soundtrack.
20th Century Boys
Noblesse, Terra Formars, The Breaker series, and Until Death Do Us Part really need to have an anime of their own.
Terra Formars and Until Death Do Us Part has more chance out of four, since they are japanese manga, compared to the two... sigh... I really wish they would have their own anime.