Thread: asking for a manga once i read but forgot its name :(

Hmm.. well, I don't know the name of the series you're looking for, but maybe I can give some recommendations...?
-Vampire Knight (you probably already know about this one)
-Vampire Game (I don't know if you know about this one or not; has some gender-bender in it...)
-Oresama Teacher (not a lot of gender-bender, but there is a little. Not supernatural, but the main characters get into fights often)
-Ouran High School Host Club (you might know of this one too; it's gender-bender but shoujo)
-Seiyuu-ka! (gender-bender)
-Rosario + Vampire (don't know if you've read this or not; it's kind of ecchi, but there is action in it... but if you like action, then I would read this one instead of watching the anime, since the best fight wasn't even in it)
-Noblesse (you might have already read this one)

I know my recommendations aren't that great _ _'|| Good luck~

Action- Gamaran (full of action scenes; real deadly scenes; martial arts), Noblesse (vampire based, action, supernatural), Btoom! (about a rpg game made into reality; killing actions)
Vampire based- Noblesse (refer above),Orange marmalade (Romance)
Gender bender- Love stage (gender bende M2Mr, yaoi)
M2M love(shounen ai)-Aitsu no Daihonmei, Boku no Ano Ko..

is the one you're talking about tokyo girls destruction? I am currently reading that, in which amasu kumi entered amazon academy to find the mystery behind her sister's death, only to find that it is not a normal school but a battleground for girls to fight over star badge.