Bamboo weapons are bamboo spears, as seen at the bamboo forest in missions 1, 5 and 9 of Commando 2. Soldiers hidden between the bamboos come out of their hideout and aim the spears at the player once he gets closer. The spears would then get stuck in whatever surface it has hit (the ground if missed the player), flicker after a few seconds and then disappear. These enemies can be shot at and killed while they are still hidden.
The Barreti can be used to constantly shooting towards the bamboos. If the bullet hits a hidden enemy, its splash effect would reveal the enemy's location, and thereby provides a good way of avoiding enemies before reaching their aiming range. Weapons like the Scorpion or the Logan-35 also provide a good indication, and also allow killing the enemy.