I've carried this a fair few times:
...but never actually got a kill with it.
From eBay it comes all silver and pretty naff looking, but some flat black Krylon and a bit of scruffying up later and it looks pretty evil IRL. TBH the times I've carried it have been with my custom loadouts, rather than my uniforms and one incident illustrates why, i think, i've never got close enough to anyone to actually use it...
It was the end phase of a game where we, the attackers, had unlimited regen while the defenders were on medic rules and then dead'n'out after their medics were hit - the winner was the team to clear out the defenders fastest. I dropped my sniper rifle and went into some undergrowth to flush any die-hards trying to add time by hiding rather than fighting. I drew my pistol on it's lanyard and put a few BB's into likely looking bushes...
...and to my amazement 2 people came out with their hands up shouting "hit" from places where my BB's could not have actually hit them and another gave himself away to a team mate of mine by wildly shooting at me on full-auto - basically they shat it!
And the moral of the story I spose: if you look like you intend to hurt people, regardless of how you may actually feel about how the game ought to be played, some people will suffer from a failure of morale, so carrying a f*ck off melee weapon, big boots, pads, hard knuckle gloves, as well as having scruffy gear but all adjusted/tied/taped up tight, no rattle/no shine stylee, and your face completely hidden, may well be worth any additional hassle it represents for the sake of intimidation.
Although if i was fitter so i was faster on my feet, for sure I too would like to play 'shame-game' with ridiculous knife kills...