Joan of Arc. This one should not need much said about it, though the details of her life have almost definitely been revised or embellished in some parts because the 'known history' of her would seem to put her as being right up on the level of Jesus between her supposed perfection, her prophecies, and her wrongful execution - nevertheless, she's always been one of my favorite historical female figures. For only a few years of activity/notoriety, she managed to become quite the legend.
Empress Theodora of the Eastern Roman Empire. Her background is not clear, as multiple conflicting contemporary histories were written about her and her husband's lives, but it is clear that she was of very humble origins (controversially so for the time). She is sometimes touted as a co-regnant (a regnant is the opposite of a regent) alongside Justinian the Great due to her unusual and intense involvement with stately affairs (her husband called her his "partner" in all deliberations, and while this almost sounds a little insulting in a modern context, it was a great compliment and quite unheard of at the time), and is perhaps best known for saving her and her husband's rule during the Nika riots in the capital. She was also a great proponent of women's freedom and rights during this particular period of Antiquity, having pushed her husband to create a number of pro-women laws in regards to legal guardianship of children, divorce, land ownership, prostitution, and for the harsher punishments of crimes against women.
Theodora and Marozia, a mother and daughter who were purportedly the lords of Rome during its darkest days post-fall. They were not particularly noble or admirable women - quite the opposite, actually - but there's something about their history and its sordid intertwining with the Papacy (seven different popes in their line!) that's always made me remember them...that, and I love both of their names.
I'm also fond of Hypatia, a noted (for the time) Greek-Roman mathematician and philosopher, who is best known for her resistance to converting to Christianity and yet continuing to freely teach both pagans and Christians and being loved by both during a particularly contentious time of religious turmoil, eventually leading to her horrific murder by extreme Christian partisans.
I'm forgetting some others that I know that I particularly like, but oh well. You can probably tell that Roman and Greek history is my favorite area of history, .
(e): Also, something that's under-known - many of the world's earliest and most notable computer engineers/scientists were actually women, something lost on most given greater male dominance in this field post-World War II and then especially so by the end of the Cold War and continuing up until now.