The blowgun is a gun that allows its user to do rapid and accurate shots. It is given to students of the School of Magic that complete the blowgun test.
Twinsen is given one of these by the rector after completing the blowgun test, when trying to become a wizard. He keeps the gun until he meets Queen Astrid and completes the test of truth, then he is rewarded with a blowtron, which replaces the blowgun.
"The Blowgun provides rapid firepower. You can reload it with small projectiles, such as berries."