If someone asked me to name someone who personified “delicate looking killing machine” or to name a woman who, based on her work, could easily beat down most men I would have to say Summer Glau. She doesn’t look like much, but has had luck, and in the eyes of many nerds, most of her success playing strong female roles.
Her first ‘major’ role was in the way too short-lived show Firefly as River Tam, a supporting character that could easily defeat over 20 men in a single fight without being hurt. She also played River Tam in the movie Serenity, the plot of which was largely based around her character. She then went on to play Cameron Phillips, a Terminator sent back in time to protect John Connor, in Terminator: The Sarah Connor Chronicles. Her latest ‘notable nerd role’ was a 3-episode stint on Joss Whedon’s recently canceled Dollhouse.
Fight scene from Serenity after the cut.