Probably something few people have read but I vote for the character of Ann Claybourne in Kim Stanley Robinson's Mars trilogy. She's the woman I found out I wanted to be when I grew up after I grew up. The storybook world needs more grumpy geologists.

Also, if we can pick more than one (and yay for being able to):
Elizabeth Moon, who is a fantastic author, and her character of Paksenarrion from the self-titled series. A seriously kick-ass female mercenary who does all the adventuring and saving the day without worrying about whether it'll make boys like her or not.