Knife as a back-up weapon

I will tell a tale on myself. When I was a patrolman I had occassion to get my trigger-finger stuck inside the mouth of a lunatic who made a yeoman's effort at chewing it off. Due to our positioning I could not access my pistol with my support-hand and I couldn't get hold of the suspect. What saved me from losing the finger was another cop. After that I always carried a small folding knife within reach of my support hand.  If you carry a handgun consider carrying a folding knife.