Off the top of my head I would have to say Boudicca, because of my own bias being of Celtic blood. But I really think that all warrior women of history are my heroes, for women in pre -modern days really had to work hard and be strong for their family. Being a warrior was a necessity for many cultures. I can only imagine the danger and struggles they had to encounter.

Ya Asantewa, Ashanti queen who led her people into battle against the British. A quote-
"If you the men of Ashanti will not go forward, then we will. We the women will. I shall call upon you my fellow women. We will fight the white men. We will fight until the last of us falls in the battlefield."

along the same lines, one has to mention Ngola Nzinga of the Ndongo, the ruthless warrior who may have slain her own brother, knowing that he could not possibly defend her people against the slave taking Portuguese, and fought them ruthlessly for years before finally being outgunned.