An acorn whistle is very effective at getting attention and amazement from friends. Additionally, it can save your life if you are lost in the woods and need a way to signal rescuers/ scare off wildlife.
First find an acorn cap. This is the brown part on top of the acorn. Make sure it is not cracked or deformed. Also the larger the acorn cap the lower the pitch.
Instruction on how to use: How to whistle using an acorn cap