A decent idea, but in reality has no real impact and doesn't make the game any better.
Yes it would make it look more real, cause in life a knife could be used again and agina.
No, because even a reusable knife you are talking about a lot of added things that are not nessacary. Why would you knife someone with a "rusty" knife to only take 50 damage. I would rather just shotgun them in the back. This tool would only benefit ppl who have no karma.