A Japanese bow (as in, bow and arrow).
The main battlefield weapon of the bushi until the 16th century, the traditional yumi was asymmetrical, composed of bamboo, and reached lengths averaging 2.3 meters, making it the longest bow on Earth. Arrows were constructed from bamboo and feathers, and the bowstring was made of silk and pine resin, giving the end result of a durable yet highly tunable instrument of destruction. While it couldn't quite rival the accuracy and penetrating power of modern composite bows, the yumi played a pivotal role on the battlefield until the undeniable effectiveness of the gun forced the Japanese to retool.
Although it is no longer used for practical purposes, the yumi is still employed in various spiritual practices. Some Japanese shamans believe that by ritualistically plucking the string and lulling themselves into an altered state of consciousness, they can make themselves accessible to communications from another world. In some Buddhist and Shinto temples and shrines, the "Hama-Yumi" ("evil destroying bow") is employed in various ceremonial practices, and may be kept in private households or shrines to keep bad vibes at bay.
Confucius believed that archery was the most effective way to shape personality; to help one shed the outer layer of the ego and realize one's true self. The art of kyudo takes this belief to a new level, incorporating Zen Buddhist and Taoist principles into a form of "standing meditation" that just happens to be centered around what seems to be a form of archery. It's quite a testament to Eastern wisdom that a tool once used to rapidly and effectively nullify human lives at a distance is now employed to bring about spiritual enlightenment and inner calm. Maybe they can help us think of a positive use for all of these nuclear weapons we've got laying around...