[Orcrist]

I think I read somewhere that Viggo lost some teeth after he jumped on that one Orc at Amon Hen. He insisted that the teeth be glued back in, and the shoot go on.

It also says in "The Making of the Movie Trilogy" that on the first day of the Ringwraiths chasing Arwen scene, one of the Wraiths fell of his horse.

I still can't think of another one.