1. GinTama
2. Girls of the Wild's (must read)
3. Fairy Tail
4. Gamaran
5. Last Game
6. Acid Town
7. Karneval
8. The breaker (and) The Breaker: New Waves
9. DOGS: Bullets and Carnage
10. [SWITCH]
11. Sekaiichi Hatsuko (BL)

besides the obvious good ones like gakuan alice, full moon wo sagashite, and kamichama karin, here are others that i think most will like that are not too 'cutesy' some peoples dunno about and they just have to know and read cus its just soo good:

Dengeki Daisy [it is romance manga but it does not have so much romance that its overwhelming. it had just right amount and comedy also! with original plot. strong lead. Ongoing.]

♥Liar Game [psychological manga it makes you think. original plot, also. ongoing.]

♥Red River [historical romance action drama. it is a serious manga with many twists and original plot and strong lead! completed.]

Wallflower [its so cute! not much romance as it is mostly comedy . but it is original . i think it is ongoing]

Skip Beat [strong funny lead character!! original plot. also moderate romance and high comedy. ongoing.]

Hana to Akuma [it is so adorable! you will fall in love with hana and vivi. she is so innocent and adorable! sweet manga with much romance and comedy.completed]

♥Kuro Bara Alice [one of the most original vampire mangas i have ever read!!! totally new concept of vampire. romance horror ongoing.]

Tail of the moon [historical romance! beautiful manga with no dull moments! completed.]

From Far Away [if you liked red river, you'll like this one! similar concept with a girl appearing in different world(time period in the case of red river). romantic, sweet and short manga. completed.]

The Bride of the Water God [original beautiful romance manga!! amazing artwork! ongoing.

♥ Black Bird [i really looove this manga! so romantic and fantasy! it's kinda sexual but i just try to ignore those parts ongoing]

♥ = highly recommended!

phew!!!! i finished! this is the best of the best! *for me* they're all so different!! please try some!

nana, ouran high school host club, fruits basket, say i love you, beck,

ookami shoujo to kuro ouji
kamisama hajimemashita
hibi chouchou
hug/kiss
ai hime-ai himegoto
hapi mari
aoharaido
faster than a kiss
naruto
kinkyori renai
sensei ni ageru.

a lot more but this i s the top 11 for me.

Yotsuba&!
A certain scientific Railgun
The Flowers of Evil
Nazo no Kanojo X
Twin Spica
Spice and Wolf
Urusei Yatsura
TWGOK
Sundome

Gantz. The best out there.

My top 11 currently (the ones I'm currently reading) are

Nisekoi
Zetsuen No Tempest
Rosario + Vampire
BTOOOM!
Full Metal Panic! Sigma
Medaka Box
Fairy Tail
Bleach
Boku wa Tomodachi ga Sukunai
Boku wa Tomodachi ga Sukunai Plus
Maid Sama

Molester man Molester man Molester man Molester man Molester man Molester man Molester man Molester man Molester man Molester man Molester man.
Read it. You'll thank me later.

Berserk
Beck
Death Note
Onani Master Kurosawa
Fullmetal Alchemist
Liar Game
One Piece
Battle Royale
Bakuman
Monster
Hikaru No Go

11s quite an odd number
Hmmm I'd recommend
Hayate no Gotoku
Ai Kora
Suzuka
Fortune Arterial
Mysterious Girlfriend X
Kimi no Iru Machi
Love Hina
Bakuman
Ai Ga Tomaranai

And thats all I can think of

1. Tenjo Tenge
2. The Betrayal Knows My Name
3. Drops of God
4. DOGS: Bullets and Carnage
5. Eternal Sabbath
6. Deadman Wonderland
7. Vampire Knight
8. Arata the Legend
9. Legal Drug
10. The Earl and the Fairy
11. Dawn of the Arcana

Special mention..Zone OO

For the mature readers:
Bitter Virgin
Minamoto-kun Monogatari
Iris Zero
Onani
Molester Man
Broken Blade
Sundance
Hetakoi

1. Kuroshitsuji
2. Pandora Hearts
3. Sankarea
4. Say I Love You
5. Soul Eater
6. Kaichou Wa Maid-Sama
7. Are You Alice?
8. Youko x Boku SS
9. Zetsuen no Tempest
10. Akame ga Kiru!
11. Ao no Exorcist

Berserk
Blue Exorcist
Bakuman
Attack on Titan
Blood Lad
Hungry Joker
Fairy Tail
HunterxHunter
One Piece
Battle Royal
Toriko

Definitely bookmarking this page!