1. Riptide (Anaklusmos): This is his main weapon - a sword that can be wielded as a normal sword but transforms into a pen when not in use. It is a gift from his father, Poseidon, and serves as a symbol of his power and heritage.
2. Camp Half-Blood Camp Half-Blood Bracelet: This bracelet is a vital symbol of his connection to Camp Half-Blood, the home for demigods. It allows him to communicate with other campers, and the magic woven into it protects him from certain dangers.
3. Grover's Pipes: Grover, Percy's best friend and satyr, utilizes his pipes for several things. He uses them to communicate with other satyrs, to control the flow of nature, and even to play music, though he's not very good at it.
4. Annabeth's Drachma: Annabeth, Percy's fellow demigod and best friend, uses a drachma (a Greek coin) to call upon a "taxi" - a pegasus, to quickly transport them across distances.
5. Charon's Coin: A special coin required to pay for passage on Charon's ferry to the Underworld. Percy obtains it from a homeless man who is actually a god in disguise.
6. The Lightning Bolt: Although not used by Percy directly, the lightning bolt, stolen from Zeus, is the central object of the book. It is the cause of Percy's troubles and becomes a symbol of the power struggle between the gods.
It's important to note that while these items are crucial to Percy's quest, he primarily relies on his quick thinking, courage, and his connection to the sea to overcome challenges.