Various parts of the Unicorn; the horn and tail hair in particular can be used in potions. Unicorn hair in general can also be used for the cores of wands. The tail hair can also be used as binding in bandages due to its incredible strength. Harry thought as he rattled off the uses in his head quickly, he could hear Henry Potter breathing start to get sporadic indicating his panic. But as Harry's mind whizzed through everything he knew of unicorns, one thing stuck out in mind, none of the uses required the unicorn to be killed, even for the horn to be used it had to of fallen off or the unicorn die of natural causes. To slay a unicorn was a horrible crime, everyone knew that. He felt his magic crackling around them as he allowed the sadness too leave as he grieved for the creature before him.