Man, I‘m chuckling at this thread - my compliments to everybody!
My two cents = Murphy‘s Law on expensive knives (you‘ll probably just lose it anyway), and Murphy‘s Guarantee on knife size (it‘s ALWAYS too big - and when it‘s not, it‘s too small ... unless it‘s a REAL Claymore sword strapped to your back ... but, I digress ...).
The Swiss Army knife is really handy for all the little stuff like cleaning/cutting your fingernails, and it‘s no coincidence that it‘s red instead of camouflage (makes it easier to find when you‘ve dropped it, and believe me - you will - tie it on).
As for a "killing knife": it‘s preferable to use your rifle, machine gun, Eryx, TOW, mortar, howitzer, or other long-distance utensil to reach out and touch somebody (after all, you can never be sure what infectious diseases you might be at risk of contracting if you let them bleed all over you, and besides - it‘s just so "icky" when they squeal like a stuck pig as you plunge it in up to the hilt, or gurgle as you repeatedly saw back and forth across their neck ... and, if I‘m turning you on, maybe you should avoid playing with sharp objects ...).
Focus your attention on learning how to be a proper soldier - and learn how to effectively use what the Army issues you. If you really want to carry extra kit, volunteer to carry lots and lots of ammo or the radio, and tuck dry socks, food, first aid stuff etc. into any space that‘s left over (and, finally, when the enemy is close enough that you think you need a knife, throw your pistol at them, then fix bayonets).
Dileas Gu Brath