Favorites in terms of looks:
Everybody in "Thunderball"
Everybody in "GoldenEye"
Everybody in "The World is Not Enough"
Everybody in "DAD"
Everybody in "QoS"
...heck, about 70% of the list
In terms of character/acting:
Diana Rigg ("OHMSS")
Carole Bouquet ("FYEO")
Maryam D'Abo ("The Living Daylights")
Michelle Yeoh ("Tomorrow Never Dies")
The only ladies I disliked were Grace Jones (I find her fugly

) and Ursula Andress (blasphemy, I know, but I didn't really care for her character

).
It's pretty darn hard to just pick one. I think I'll have to go with my favorite ever since high school...Maryam D'Abo from "The Living Daylights." A nice mixture of good looks and good personality.