I think that Harry will kill Voldemort. I know that some people think that it could be Neville, but I doubt it. It'd be a sweet twist, though if the prophecy was talking about Neville, although I say its Harry. The strongest evidence that makes me say Harry and not Neville is the fact that it says in the prophecy, "...and the Dark Lord will mark him as his equal, but he will have power the Dark Lord knows not..." Voldemort has not marked Neville as his equal, just Harry.