Vala Mal Doran, a former Goa’uld host who’s now a scheming con artist/space pirate.

While her amorous attraction to Dr. Daniel Jackson is clear, her ultimate agenda remains a mystery.

She was apparently a former host to a Goa'uld named Qetesh (fittingly, based on the sex goddess Qetesh of Chaldean and Egyptian mythology).

::Vala on Wikipedia