Tokyo Ghoul
My only issue is that the story writing can be very messy. It's hard to keep up with who's who
One Piece
One of my favorites. Although the beginning was a little bumpy for me, what really held me on a tight grasp was the One Piece world. It has pirates vs marines, a corrupt world royalty that enslaves innocents and whom the marines must protect, a variety of living beings such as fishmen, mermaids, angels, talking animals, giants and dwarfs. The arc with Vivi (the complete alabasta arc) is suuuuuuuuuuuuuuper long (that arc was the one that felt longest to me lol) but getting through it to see the rest of the story is really worth it. Some chapters are annoying but there is always a chapter that makes you feel extremely happy that you're a part of this.
Devil and song
The ending was a bit unsatisfying
Elfen Lied