Sally Hardesty (played by Marilyn Burns) is arguably the first Final Girl of modern slashers. But it's not just that she was the last man standing in Tobe Hooper's seminal The Texas Chainsaw Massacre (1974). It's that she fought mightily for - and earned - that title.
You know the story by now: Sally, her brother, and a handful of friends travel across rural Texas to visit their family home and discover a family of bloodthirsty cannibals living nearby. The cannibals, led by Leatherface, pick off the kids one by one, except for Sally. Sally spends the final thirty minutes - a full third of the film - fighting for her life. She is tortured and terrorized, runs and screams - boy, does she scream. Sally does enjoy a bit of luck, if you can call it that. Her friends were all killed outright; the Sawyer family chose to keep her alive to play with. Perhaps it is because she showed such fight. Early on in her ordeal, Sally leaps out a second-floor window without a moment of hesitation, all in the name of escaping. And she does escape, but only temporarily, when a local she goes to for help turns out to be in cahoots with the Sawyers and brings Sally for their demented family dinner.
Sally escapes once again (and again, it is by jumping through a window - first floor this time), and makes it to the main road, where she jumps into the truck bed of a passing motorist. Leatherface is still hot on her heels, but she is younger and clearly in better shape, though the viewer is left to wonder how long could Sally have run before Leatherface would have inevitably caught her.
Sally is the earliest example of the Final Girl; the argument could be made that she is one of the weakest Final Girls. As the Final Girl has evolved over the decades (as with the female's role in films), she has gotten stronger and almost always kills her attacker. Sally does not. She screams, she runs, she fights, and she survives. But in Sally's mind, escape is the only option. With an entire family of lunatics out for her blood, I have to imagine she made the right choice.