I'd like to request for a knife with blackwall on it.
For visuals: it's not too much of a unrealistic expectation, it would be nice that it had a unique design(that fits the world of cyberpunk, that is)... But a simple color variation of an existing one(like a black version of the Blue Fang, and with blackwall effect on it) would be enough.
For gameplay: It would have mostly regular stats like every other knife, but with the difference that headshot kills trigger the blackwall death animation. Could put a penalty on the return time after a blackwall kill. Even add a stat so it takes 10%-15% of V's health. For balance purposes.