Goddess Sword is able to be considered a sacred sword as the Skyloftians that are aware of it's existence revere it and treat it with worship like respect. As it’s a gift from the goddess Hyla herself, this also marks the item as a sacred artifact through direct association with a diety.
Goddess Harp and three of the songs are sacred because the Harp is thought to be an actual possession of the Goddess Hyla that was given to the Skyloftians, and the songs are from the three goddesses Farore, Din and Nayru.
The Sailcloth, though just a normal cloth woven by the hands of the mayor's daughter. It is not in and of itself a sacred object, but when coupled with what it means and represents, it’s a symbol of their goddess and the blessings she’s given. Presented with the explination: "The blessings of the goddess drift down from the heaven aloft a sail. Which I now pass on to you."
A divine and holy blessing placed upon the Master Sword upon forging as a sign that the goddesss were on the hero's side.
Objects found and used by the Hero of Skyward Sword that are considered Sacred.