Both a knife and a gun are considered to be lethal force. If a situation occurs where a knife is deemed to be reasonable force, then you have let the enemy get too close. I see your point on how some individuals have multiple optics and flashlights, but we should be reducing the crap we throw on our weapons, not adding more crap like this that only serves a purpose if you make a stupid mistake. If a hostile gets close enough for you to stab him, then he is close enough for you to muzzle strike him, back off, and shoot him! A bullet will incapacitate an aggressor much faster than a knife will.
Originally Posted by Jim D
"Every normal man must be tempted at times to spit on his hands, hoist the black flag, and begin to slit throats." - H. L. Mencken