Experts argue whether or not you should fight back against a grizzly or play dead. But all the experts agree that you should fight back against a mountain lion. They can be beaten off by the unarmed because the animal doesn’t want to risk even a moderate injury because (in the wild) such an injury is often fatal. So definitely kick and punch all you can. If you can manage to draw a knife, pistol, or other weapon, more power to you. But let’s assume that the cougar saw you first and attacked you unawares, because that is 99.99% cougar attacks happen. If he is already on you, your shotgun is useless and probably your pistol and knife as well. Good luck drawing them with a cougar gripping your neck. I don’t know, maybe you can draw and shoot or stab without hitting yourself, but probably not.
If you see and confront the cougar BEFORE the attack, he will almost always move off. You don’t need a gun, just wave your arms and shout. This may or may not work for a bear, but it isn’t a bad idea to try anyway. But for a cougar, it almost always works.
But again, the first line of defense is to be aware of your surroundings. Don’t be an easy victim! Cougars look for easy prey, and if you appear alert you can deter the cougar even if you don’t see it. The lion WILL see YOU. If he thinks that his chances of a surprise attack are slim, he will go elsewhere. Most cougar attacks are on joggers who are running in an endorphin daze, oblivious to their surroundings. An alert hiker is a safe hiker.
When I was a lieutenant in the USMC, our Col had us read “A Soldier’s Load and the Mobility of a Nation”. The short version is that if you carry extra pounds, you are slow and tired and you are not thinking clearly. This is not a good way to stay alive. If you are carrying pounds of weapons and other survival gear that you don’t need, you are simply increasing the chances that you WILL need them. Now obviously we needed some of those weapons and gear in the USMC. But do YOU really need it? What will the lion see? He will see a slow, erratically moving, tired, staggering, and dazed guy carrying a bunch of junk that appears to have no useful purpose. Looks like dinnertime!
Think this over the next time you weigh your pack before your trip. Then try taking half your stuff out. You will be safer. My pack these days is usually well under 30 pounds. I can’t for the life of me understand anyone carrying more than 40 pounds.