Tom Bombadil - A mysterious character who lives in the woods outside the Shire and is married to a river nymph named Goldberry.  Twice he saves Frodo and his companions from danger; first from Old Man Willow in the Old Forest, and then from the Barrow-wights in the Barrow Downs.  He is ancient being, even rivaling the Ents in age.

"But I had forgotten Bombadil, if indeed this is still the same that walked the woods and hills long ago, and even then was older than the old.  That was not then his name.  Iarwain Ben-adar we called him, oldest and fatherless.  But many another name he has since been given by other folk: Forn by the Dwarves, Orald by Northern Men, and other names beside.  He is a strange creature..." ~The Fellowship of the Ring, Book II,  chap. 2 (The Council of Elrond)