what should i watch next?

Horror

-Another
-Le Protrait de Petit Cossette ((3EPS))
-Elfen Lied
-Death Note
-Deadman Wonderland

Shoujo

-Kimi ni Todoke
-Ouran High School Host Club
-Ano Natsu no Matteru
-La Corda d'oro
-Skip Beat
-Vampire Knight
-Eden of the East
-Angel Beats
-Hakuouki
-Natsuyuki Rendevzous
-Uta no Prince-sama
-Otome Youkai ZAkuro

Shounen

-Naruto/Shippuden
-Bleach
-Kuroshitsuji
-Durarara!!
-InuYasha
-Kuroko no Basket
-GetBackers

Other

-WAGNARIA!!/WORKING!! ((shounen/shoujo))
-Summer Wars ((MOVIE))

Well just from Hell Girl it doesnt give me a whole lot to go on but here goes..

*Darker Than Black
*Death Note
*Blue Exorcist
*Mushi-Shi
*Angel Beats
*Nabari no Ou
*Red Garden
*Ghost Hound
*Ghost Hunt
* Pet ショップ of Horrors (only 4 eps)
good luck ;)

あなた should watch Angelic Layer! Im watching it right now on Youtube! Its fantastic and its in English sub または dub.
Its based off a マンガ series によって CLAMP!

Well, あなた can try some of these:

- Soul Eater
- Death Note
- Shaman King
- Fullmetal Alchemist/Fullmetal Alchemist Brotherhood
- Blood +/Blood C
- エンジェル Beats
- Higurashi
- Katekyo Hitman REBORN!
- K Project
- Naruto/Naruto Shippuden
- One Piece
- Bleach
- Fairy Tail
- Hetalia
- K-ON!
- Another
- Anything from the "Tales of..." series (I liked The Abyss)
- REC
- Starry Sky
- Fruits Basket
- Pandora Hearts
- Clannad
- ジン Tama
- 黒執事 (Black Butler in English)
- Danshi Koukousei no Nichijou

And many, many more. These are just some of the 人気 ones. And they are pretty awesome starter アニメ (mine was Naruto). あなた might wanna watch some classics, too. Like Sailor Moon または Dragon Ball Z, to set a example