So, I've been keeping a "killboard" of Heroes for ages, tracking both killers and methods, and I thought I'd post updates on it.
Sylar has long dominated the killboard, although he did slip behind Maya Herrara at the end of Volume Two. He currently has killed 44 people onscreen, although he has also had one of his kills undone (Charlie). Maya is still holding in second with 18 kills, with Tracy Strauss and Samuel tied for third with 13. 106 people have been killed with powers, while only 41 have been killed with weapons.
Noah Bennet has finally noticed that for Heroes' reigning badass, he's ranked fairly low. The flashback killing of Becky Taylor's dad brings him up to four, but that isn't enough to overcome the fact that Matt Parkman has killed five people on the show (he turned all those commandos against each other with telepathy in "Trust & Blood".
Danko's reported killing of Joseph brings him up to three. I'm holding off on assigning a killer to Mohinder until we actually see the death or it is described.
Hank was an odd case, but I've given that kill to Sylar, given that it was Sylar's mind, even if it was Matt's body. This is also the second time Sylar has killed someone named Hank - there was a Company doctor back in Season One, who also posed as Claire's biological father.
Finally, guns have finally outstripped poison emission as the second most common cause of death (19 vs. 18), though telekinesis still rules at 31.