I've always saying that Basilisk, Touka Gettan, School Days, Hell Girl 1,2,3 , Code Geass: Lelouch of the Rebellion, Trinity Blood, Myself;yourself , Loveless, Neo Angelique Abyss, Skip Beat, Romeo X juliet, Siunkoku Monogatari, Itazura na Kiss, Kimi ni Todoke, and Yamato Nadeshiko Shichi Henge. Just try watching one of these. i'm sure you'll eventually like it.
woot for Vampire knight Loveless( for over 15's) Fruits Basket Haibane Renime Chobits( for over 16 yes i watched it when i was 11 but don't make the same mistake i did, the stories crap but it's funny just to laugh at and the animations are fantastic) but really watch loveless it's one of favs( i cried when the 1st season finished i want a 秒 season)
it depends on you,but I'll suggest a few that I know,some of them I didn't like myself- >if u want a hilarious & entertaining anime,I'll say OURAN HIGH SCHOOL HOST CLUB,SPECIAL A & FRUITS BASKET >if u like the one with lots of thinking,I think between CODE GEASS,CANAAN & DARKER THAN BLACK >if u are looking into social 或者 sentimental theme,it will be FRUITS BASKET,OURAN 或者 KOBATO >if 你 want to drool over hot guys,its VAMPIRE KNIGHT,OURAN 或者 PRIMO PASSO LA CORDA D ORO >if u favor moe girls,then NEGIMA,SHUFFLE 或者 THE MELANCHOLY OF HARUHI SUZUMIYA >if u wanna see awesome fight scenes,watch GUNDAM OO,FULLMETAL ALCHEMIST 或者 CODE GEASS