I had a strong feeling making such a delicate knife just a one-time pickup is such a waste of its beauty. So instead of a one-hit kill, the knife will be stabbed onto the target player and then cause a small explosion that kills the player. This also explains why knives are one-time-use consumables.
Will this makes murdering harder as they have 2 seconds to respond? Yes. But it will be more fun to see how people react in that 2 seconds when they know they were stabbed.
Player A: *Stab*
Player B: "You $%*^&%"
... *Explode*