Obvious spoilers for Deathly Hallows..
Excerpt from Slytherincess' answer to Why was Wormtail made a servant ?
Voldemort enchanted the silver hand to kill Wormtail if Wormtail showed the weakness of mercy.
Is there any source for this ? At one point, Dumbledore tells Harry that a life debt between two wizards is something very powerful (at the end of PoA I think). I always assumed that Wormtail wanted to kill Harry but that some kind of old magic prevented him from doing it.
So... Did Voldemort really enchanted it ? If so, why didn't the hand just kill Harry when it had the occasion ?
ETA : I just found this quote by JKR :
When Dumbledore said to Harry "Voldemort won't want a close associate who is in your debt", I wasn't implying by that there was any kind of magical bond there.
I throw my theory away :p see the accepted answer for more details