From Sonic Retro
The Volkan Cannon was first introduced in Sonic Adventure 2. It is one of the main weapons of "Tails"' Cyclone and Dr. Eggman's Egg Walker. It fires a small metal projectile and can destroy wooden crates. It can be upgraded (with the Bazooka for "Tails", and the Large Cannon for Dr. Eggman) to destroy steel crates as well.