Nemean Lion's Pelt

The Nemean lion's pelt is a magical spoil of war formerly owned by Heracles (or better known as his Roman counterpart- Hercules) after he used the lion's claws to skin him as one of his 12 labors, and later by Percy in The Titan's Curse after his plan allows Zoe to kill the Nemean Lion, leaving its pelt behind.

The Titan's Curse
Although in ancient times it remained a lion's pelt, in modern times it becomes a bulletproof and generally weapon-proof leather jacket. It was obtained when Percy used foul tasting space food from the gift shop at the National Space and Air Museum in the Smithsonian, souvenir shop in Washington, D.C. to distract it while Zoë, Artemis's lieutenant in the ranks of the Hunters of Artemis, shot the inside of its mouth with arrows. Even though Zoe was the one to kill the monster, she gave the pelt to Percy because he came up with the idea and she would of lost to the lion without his help. The pelt is later used as an offering to Poseidon so that Grover and the ophiotaurus will make it back to the East coast safely.

Hercules
The Nemean lion's pelt was once worn by a son of Zeus, Hercules, in ancient times. Little is revealed about what he did with it in the book, but in Greek Mythology he wore it as a cape/armour of sorts. The pelt later returned magically to the Nemean lion once the monster was reborn in the Underworld.

Percy Jackson
Percy Jackson later won the pelt after defeating the lion in the National Air and Space Museum in Washington, D.C. in The Titan's Curse; it proved useful to him several times in battle with the skeletons that the Titan General, Atlas, sent after him and Thalia, and it was also quite fashionable, according to Thalia.

Poseidon
Percy later tossed the pelt into the sea as a sacrifice to Poseidon when Grover says that he can take the Ophiotaurus that the Titans were chasing back to Long Island and Olympus itself. It is unknown whether the god received it or it returned to the lion itself when it is reborn.