First one I'll cover, name is NoobKiller.
Challenging/taunting players constantly (and not doing very good at it) He lives in the USA, and I noticed he was under a proxy.
Second One, name is Yak
There are actually 2 Yaks, one of them is a disgruntled Ecuadorian player, well both are from Ecuador. Their ISPs are different, only visible difference is the cheating Yak wears Red Othello skin (skinhack?) and the other one is Blue Blake.
The non-cheating Yak does have bad behavior, accusing players that don't even use sniper that often of cheating. (Me lol, it was getting so bad I had to enter one of my aliases, Robert_Plant), challenging players, but using different players instead of him.
So if you can take care of these 3 nuisances I would be pretty happy.
(BTW, it was only me who saw NoobKiller, but Shai and Rubino were there to see the fake Yak)