Fish and Game officials say if you run into a mountain lion, do not approach it or run away. They advise facing the cat, making noise and trying to look bigger. And if attacked, they say, fight back.Just don't fight back with anything - like a .45 or a 44 magnum - that might really be effective.
Your average house cat, can inflict some pretty substantial damage. I hate to think what a cat the size of a large dog could manage.