Yari (槍) is the term for one of the traditionally made Japanese blades (nihonto) in the form of a spear, or more specifically, the straight-headed spear. The martial art of wielding the yari is called sōjutsu.
The Shoninki shinobi manual mentions using a spear to lean against the wall a shinobi is descending from and sliding down to break the fall. Another way to do it is by using the spear to jump down by letting it hit the ground first for a lighter landing. The manual also mentions sabotaging the enemy's arsenal by by snapping of their yari's heads.