Kay, without trying to involve my waifus or potential waifus, here's who I think were the most awe-inspiring characters when I first saw them.
In no particular order:
Shizuku Sangou (Kämpfer)
Esther Blanchett (Trinity Blood, I think she'd be my Top 1, if Top 5 there is)
Misaki Kirihara (Darker Than Black, especially in that chinese dress. Too bad she's only a second role in that anime)
Akiyama Mio (I'm no K-ON fanboy but I have to admit she's lovely)
Ayanami Rei (Neon Genesis Evangelion. One of the firsts)
Ikaros (Sora No Otoshimono, this goes without saying)
Sando/Chun Hyang from Shin Angy Onshi
it's a pain to find a decent picture of her, those who've read this will understand
Finally, I'd like to insist that this is not a top of my favourite characters (except one). I had to put a lot of effort not to put sum of my waifus .-. .