If you forgot your knife, try your ballpen.
There are a few cases where people have successfully fought off an attacking mountain lion with a pocket knife. The victims usually end up on the ground with animal, and the cats are relentless until killed or severely injured. I just came across this attack from 2007 in California. A 65 year-old women used a ballpoint pen to fight back against a mountain lion that was attacking her 70-year old husband. Here is the pertinent part of the story as reported by Paul Bright of Associated Content.
Jim Hamm of Fortuna, CA, and his wife, Nell, were enjoying a hike at the Prairie Creek Redwoods State Park near the California north coast when a female mountain lion suddenly pounced on him. His wife, walking ahead of him was unaware of the attack at first until she heard him call for help. Nell Hamm quickly attacked the lion with whatever she could get her hands on as Jim’s head was in the lion’s mouth.
Nell first grabbed a branch and began to beat the mountain lion, but it wouldn’t let Jim go. Jim told her, “I’ve got a pen in my pocket and get the pen and jab him in the eye,’” she said. “So I got the pen and tried to put it in his eye, but it didn’t want to go in as easy as I thought it would.” When the pen failed to work, Nell picked up the log and began to beat the lion again. The mountain lion released its grip, stared at Nell, and slowly walked away as she screamed at it.