Okay, normally, I NEVER complain of ks. I'm a complete believer in kill-security. As long as they die, I don't care who gets the kill. Not to mention, I play a lot of champs, who frequently, "kill steals" everyone. Caitlyn, Ashe, Lux, all with long range ults. And the other person who my team is trying to kill, has completely escaped...and there's no way my team can catch them. But I ult, get the kill, and non stop hear of "ks!" the whole game.
Anyway, back to my point...there are SOME cases of obvious ks trolls, and I can't stand those people. Personally, as I've said, i DON'T care who gets the kill. But when I'm Sivir, and I've completely wiped out an Olaf's health, and a ww comes flying from jungle to last hit Olaf...when I'm not in any trouble at all...that's pretty irritating. And mostly because, this ww I'm speaking of, he was(on 3v3) jungling the whole game. And would only come out of jungle to last hit champs. NOT gank....just literally to last hit them. And run back into jungle. Wouldn't push or anything.
And I've experienced a couple of these people(...sadly, they're always ww/udyr -.-).
This is just an added on thing: If I'm about to gank someone, or help my team mate. If my teammate has wiped the person health down, I will jump out and run in front of the enemy, and will only attack, if i'm 100% sure my team mate can't get the kill.
I just wish everyone could be this thoughtful. :/