Sif
One story known of Sif is that Loki cut her hair off as a practical joke while she was sleeping. When Thor saw this, he threatened to smash Loki if he did not replace her hair. Loki received strands of gold from a pair of dwarves that would attach to Sif's head and grow like normal hair.
"Sif." Encyclopedia Mythica from Encyclopedia Mythica Online. <http://www.pantheon.org/articles/s/sif.html> [Accessed February 12, 2004].