Froggs wrote:Seven horcruxes, seven books...perhaps we have been "introduced" to a horcrux in each book, so we already know all but one...Book One would have been LV himself, and so on...Just a guess, I really have no idea what the other horcruxes are...
It's a theory Froggs, and would be the best indicator to Nagini being a horcrux. It only falls down in a couple of places, one of them being PoA which introduces no significant objects, although it does introduce Peter Pettigrew who gains a magical hand at the end of book 4 which could be a new horcrux.
It, as a theory, also seems to rule Harry out but it could then be argued that the piece of LV that survived the original attack on Harry didn't have a soul but was just the essence, meaning then that Harry's scar could be a horcrux. (Possibly created with the soul that LV tore out of himself with the failed killing curse) That would lead to the rebirth of LV in GoF using one of his horcruxes up in re-creating him. (probably Nagini)