Kaiten, a torpedo invented and used by Japan in the last months of World War II. However, it wasn't technology or weaponry advancements that ended the Kaiten's existence - it was the ultimate death of the soldiers who controlled the Kaiten.

The Kaiten wasn't like any other torpedo in use during World War II. These submarine torpedoes were manned by soldiers in the Imperial Japanese Navy, who drove these suicide craft right into their enemies. It was a weapon created to shake the enemy to their very core, its name chosen because it meant "the heaven shaker" or "the turn toward heaven" in English.

When the Japanese military felt they were losing control and their chances of winning the war - they turned to the Kaiten, despite its high human price.

Source: warhistoryonline.com