In Norse Mythology, Nagifar is the ship that will be used by the giants when they attack Asgard at Ragnarok. It is built from the fingernails of dead men by Hel and will be launched from Jotunheim filled with Jotuns, armed and ready to fight the Gods.

Every time you or any other human trims your fingernails, the construction of Nagifar is delayed. It is known as "the ship with rivets".

Sources:
http://www.sunnyway.com/runes/gods2.html
http://www.meta-religion.com/World_Religions/Ancient_religions/Europe/norse_mythology.htm