Disclaimer: Harry Potter belong to a certain blonde british lady, not me!!(though I'm blonde too. But not brittish, so it can't be me ;)
This is just me ranting..
Harry is the last one of the pieces that holds Tom Riddle soul.
When Voldemort cast the killing-curse on Harry as a baby,
the protection created by his mothers death,
rebounded the avada kedavara onto Riddle.
This rebounding accidently creating an horcrux,
sealed by the lightning-shaped scar on Harrys forhead.
Tom Riddle had already created six other horcruxes,
and he belived that seven was the ultimate magical number of horcruxes.
Horcrux 1: The Diary, just a test. An experiment.
Horcrux 2: The Marvolo Ring.
Horcrux 3: His Mothers Necklace, Regulus Augustus Black stole it.
Horcrux 4: Helga Huffelpuffs badger-cup.
Horcrux 5: Something of Gryffindor or Ravenclaw.
Horcrux 6: His pet-snake, Nagini.
Horcrux 7: Harry Potter.
Slughorn said that noone had ever tried to split their soul in more than two pieces before.
When Voldemorts soul split into seven pieces,
his long wanted immortalety was finally a factum.
But immortalety as all other things,
comes with a price.
The price Voldemort had to pay,
was the loss oh his mortal body.
This explaines the need for Harrys blood in the potion that "ressurected" Voldemort
(The "ressurection" mearly gave him back him mortal flesh),
and the duelling insident.
How can one part of an soul possible duel against another part of that same soul,
without creating some form of magic fenomena out of the ordinary?
This also explaines the visions,
that pieces of an torn soul calls out for his missing parts,
trying to connect on a sub-conscious level.
Both Nagini and Voldemort has been in contact with Harry,
Nagini when she attacked Artur Weasley,
and Voldemort on various occasions.
To kill Voldemort for sure,
Harry must in the end,
commit Suicide.
"The one with the power to vanquish the Dark Lord approaches...
born to those who have thrice defied him, born as the seventh month
dies... and the Dark Lord will mark him as his equal, but he will have
power the Dark Lord knows not... and either must die at the hand of
the other for neither can live while the other survives... the one with
the power to vanquish the Dark Lord will be born as the seventh month
dies..."
Written by Aim.