The Ramirez Katana
Connor took the sword of Juan Sánchez Villa-Lobos Ramírez, which he had presumably kept since his friend and mentor's death in 1547 (at the hands of the Kurgan).
The sword was totally unique: A steel katana with a carved dragons head ivory handle and an ornate gold hilt. Even the solid sheath was adorned. Brenda Wyatt remarked the complexity of the blade's forging was centuries ahead of its time.
It was made by the legendary sword smith, Masamune, as a wedding gift to Ramirez when he married his daughter Shikiko. Ramirez cherished the sword (just as he'd cherished his wife), remarking that the weapon was "one of a kind, like his daughter [Shikiko]."
During The Gathering in 1985, Connor used the sword in battle, successfully defeating the Kurgan (in their final battle) and claiming the prize. The sword stayed in his possession for the next ten years, until the blade was shattered by the resurfaced Immortal Kane. Connor returned to Scotland, where he managed to forge a new blade with the help of Dr. Alex Johnson. She provided him with a block of high-carbon steel (forged by Connor's second mentor, Nakano, in the 16th century)
Connor would go on to wield the sword in battle once more in 1995, where he ultimately defeated Kane in their climactic final battle.