I'm gonna give the #18 spot to "The Pendant of Kamehameha." While it was memorable for Robbie's speed, Tina's going up to the Gargoyle Room, and the ending, there are more memorable runs than this. I'm sorry if I've gotten rid of this one too soon, but this is seriously getting hard now.
1x03 - Galileo's Cannonball
1x06 - The Golden Cricket Cage of Khan
1x08 - John Sutter and the Map to the Lost Gold Mine
1x37 - Lawrence of Arabia's Headdress
2x13 - The Lucky Medallion of Atocha
2x14 - The Applewood Amulet of Emiliano Zapata
2x16 - The Lucky Pillow of Annie Taylor
2x18 - The Enormous Iron Nose Ring of Babe
2x34 - The Golden Earring of Henry Morgan
2x35 - The Milk Bucket of Freydis
2x37 - The Levitating Dog Leash of Nostradamus
2x38 - The Broken Wing of Icarus
3x07 - The Secret Map of the Bandit Queen
3x17 - The Discarded Seal of Ivan the Terrible
3x23 - The Lost Hornpipe of the Pirate Captain
3x28 - The Mussel Shell Armor of Apanuugpak
3x40 - The Jewel-Encrusted Egg of Catherine the Great
#18: The Pendant of Kamehameha
#19: Henry VIII's Great Seal
#20: The Mask of Shaka Zulu
#21: The Much-Heralded Helmet of Sir Gawain
#22: The Dragon Lady and the Blue Pearl
#23: The Metal Beard of the Egyptian Queen
#24: The Broken Trident of Poseidon
#25: The Priceless Portrait of the Polynesian Girl