Mizore is definitely near the top of my list. She's straight up sexy, and has a hilarious personality to boot.
Now, it's my turn. I'd like to point out that a character can be physically attractive, but it's hard to connect with the character if they're one-dimensional. So my list consists of those whom are not only attractive, but are awesome characters. Oh, and I won't mention what's already been mentioned. I'm sure most of us here agree that Mizore is straight up awesome...and sexy.
I'll be doing it by anime/manga series to save space.
Ichigo Morino from Onegai Teacher! and Onegai Twins!
It's hard to see why Ichigo from Onegai Teacher and Onegai Twins is attractive without some context. But, in actuality, she appears to be a very petite Highschool Student but she's actually a 21-year old woman who lives alone, but due to a condition called "Standstills". As a result, she's actually very mature and has a introverted shy personality. Despite being quiet, she's quite endearing, and later in the series, she opens up her much more playful personality. I find her attractive purely for her character, not necessarily how she looks...but she is still pretty cute though.
Koyomi Mizuhara from Azumanga Daioh
I mean, come on, it's Yomi! She's cute, smart, athletic, loves food, and isn't perfect. She's quite the character in Azumanga Daioh, and isn't a foil character either. I don't really know why she's so attractive, she just is.
Makise Kurisu and Suzuha Amane from Steins:Gate

Two very attractive women from an anime about time travel. Go figure.
Tsubasa Hanekawa from Bakemonogatari
In an anime that has a lot of fanservice, you'd think that you'd be desensitized to it all in a given series, but Tsubasa is super sexy, especially in cat form (as Black Hanekawa). But it gets hilarious in this scene:
http://www.youtube.com/watch?v=wyV3SksAKRYThat scene had me rollin'!
That's all for now, you can probably count in seeing me here more often later on.