Yuki Kajiura for all those gorgeous classic-influenced rock gloriousness - Fate/Zero, Puella, Kara no Kyoukai, even her work with bands Kalafina and Fiction Junction ahhhh <3
Yoko Kanno with Zankyou no Terror, Cowboy Bebop!! And can't forget Joe Hisaishi and his work with Ghibli <3
Absolutely ADORE their work, to die for. * fangasms*