Eye of Ra amulet

A replica of the Eye of Ra, unburied and snatched away by young Catherine Langford during her father's archaeological dig at the Giza plateau in 1928. She carried it with her all her life. Before the first team went through the Stargate in the mid 1990s Catherine gave the amulet to Daniel Jackson to take with him to the other side. There it was temporarily taken by Ra, who wore it to enforce his power -- until Jackson managed to get close enough to retake the necklace.

Jackson, deciding to remain on Abydos, then gave the amulet to Jack O'Neill to return to Catherine. This was not the last he saw of it, however. After Catherine's death it was among the possessions in her estate that she had left for Daniel.

KEY EPISODES

"Stargate" the Movie - Langford gives the Eye of Ra amulet to Jackson to take with him on his journey through the Stargate.
The Torment of Tantalus - Jackson discovers Langford still carries the amulet and never takes it off.
Full Circle - The ascended Jackson shows the replica of the Eye of Ra to O'Neill, explaining that the Eye of Ra crystal in fact looks like the amulet.
Stargate Origins - Young Catherine wears her pendant to Abydos, where the local inhabitants are convinced that she and her companions are emissaries of Ra.