And it doesn't make sense to me. My amarr dust soldier can shrug off shots from a defensive turret or stand right by a grenade as it goes off, but stab him with a knife and he drops?
Well, a nova knife isn't just a bit of metal, but shenanigans involving plasma and graviton generators and a whole load of technobabble, so maybe. Of course, that just leads to the question why if that technique is so effective in penetrating DUST armor, why don't they tip a small missile with it or something.
Yun Hee uses these extensively. If you use a Minmatar scout suit and advanced knives you can one-shot (well, technically two-shot; they're used in pairs) heavies with even moderate skills, putting their power level well ahead of even a plasma shotgun. The main problem is getting close enough.
If I recall correctly, the item description explains it as a knife that reinforces its strike with a plasma charge. The visual effect is ambiguous-- you see the knife arcing electricity, but there's none of the orange plasma flare you get from most of the game's plasma weaponry.
My guess is that the knife functions like a sort of plasma variant of a HEAT round, striking shield and armor with the typical force of a nano-augmented supersoldier lashing out with a knife, then venting superheated, ionized gases through the breach.
Owie. Not something you'd want to be on the receiving end of.
Also yet another weapon you probably don't want to use without a dropsuit*. The thermal backwash has got to be
fierce.
Mind you, even if we weren't talking about horrible sci fi plasma blades, we'd still be talking about clone soldiers being downed with knives
by other clone soldiers. There's a lot of strength behind that blow, and then there's the further augmentation provided by the suit. Pistol-whipping a dropsuit works just fine if you can punch like a railgun.
* ... if you even could. All DUST weapons, including nova knives, have dropsuit CPU requirements, even if they don't need PG. This incidentally helps to explain why you can't just pick up weapons on the battlefied-- they're installed as part of the suit, and probably inoperative if detached. Granted, even an inoperable nova knife is still a really big knife.