Determining the "best" sword in history is subjective and depends on various factors such as the specific criteria, cultural context, and personal preferences. Many exceptional swords have been crafted throughout history, each with its unique qualities and advantages. Here are a few notable swords that are often regarded as among the best:

1. Japanese Katana: The katana, a traditional Japanese sword, is highly regarded for its craftsmanship, sharpness, and balance. It has become iconic for its elegant design, versatility in combat, and historical significance within samurai culture.
2. European Longsword: The European longsword, used during the medieval period, was a versatile weapon known for its effectiveness in both cutting and thrusting. Longswords were crafted with quality materials and demonstrated excellent balance and durability.
3. Damascus Steel Swords: Swords made from Damascus steel, a type of steel produced in the Middle East from around 300 to 1700 CE, are celebrated for their exceptional sharpness, durability, and distinct patterned appearance. The craftsmanship and quality of Damascus steel swords contribute to their reputation as some of the best swords in history.
4. Ulfberht Sword: The Ulfberht sword is a type of Viking sword known for its high-quality craftsmanship and advanced technology. These swords, often inscribed with the word "Ulfberht," were made of superior materials and demonstrated superior strength and sharpness for their time.
5. Chinese Jian: The Chinese Jian is a straight, double-edged sword known for its precision, balance, and elegance. These swords were crafted with meticulous attention to detail and were highly regarded for their effectiveness in both offense and defense.

It's important to note that the concept of the "best" sword can vary depending on personal opinions, historical context, and the specific criteria being considered, such as craftsmanship, historical significance, cutting ability, or cultural importance. Each sword has its own merits and cultural significance, and the choice of the "best" sword ultimately depends on individual perspectives and preferences.