Full Moon wo Sagashite ! This mostrar may seem like your "cute average happy show" but its really not. it has a pretty sad premise, and while there are some cute parts the last 10 o so episodes are really dark and depressing, but the ending is really good and made me cry TT_TT I whole heartedly recommend it to anyone looking for a good romance, comedy, drama, etc. :D
As of right now, it's JoJo's Bizarre Adventure. I got into the series last week, it's sad that I can't seem to find any fans. The series itself may be old but it has a great plot, characters, and the autor has the guts to kill off it's main characters and have new ones rather than the first protag live throughout the whole series, I rarely see anyone talk about it.
My answer is Dusk Maiden Of Amnesia=) I really loved the whole serie it's basic genre is horror but it's ecchi and comedy in the first episodes when the story goes on it becomes darker and más important it's my #1 anime of all time(for now) but i didnt see anybody talking about it so far=\