Crafted from a Thick Pipe and Artillery Notes, the Buster Cannon is quite a weapon. Its total upgrade costs cap out at a rather large sum of 930,000z. It’s pretty easy to upgrade at first, but as you begin to level it up, the price really goes up! It’s worth it, however, and there are some pretty nice ways to gain zenny in the game.
The Buster Cannon fires a blue shot that quickly travels across the screen, hitting anything in its path. The shot is semi-homing as well; if you were pointed in the general direction of the enemy, you’ll hit it. They are also guard-breaks as well, which is always nice. It also doesn’t create an explosion like most weapons do; it simply hits the target and dissipates, making it an ideal sniping weapon. Note that Megaman will get pushed back a short distance after the shot is fired, which is a pretty nice touch (MMIV’s charge shot, anyone?), just make sure there’s no lava (or other damaging floor hazard) behind you when you use this!
The greatest aspects of this weapon are its speed and range. This is the best way to deal with Glyde’s Draches (or whatever he calls them) on Nino Island; you can take them out in one shot provided you don’t have an S-License. This is also the ideal weapon for preserving the statue during the battle with Teisel’s Blitztrieg (yet strangely the cutscene doesn’t recognize the fact that you saved the statue), and it’s also the only weapon outside of the Hyper Shell that can hit the back of the Gemeinschaft (Bonne car) without you having to chuck Servbots at it.
There really aren’t too many downsides to the Buster Cannon. Its damage isn’t as high as some other weapons are, and you may end up swapping this out for the Hyper Shell in some cases. While your feet are nailed to the ground when using this, it does fire pretty quickly (unlike the Hyper Shell), so that helps it out.
Conclusively, the Buster Cannon is a great weapon that is pretty usable in most situations. It’s effectively the charge shot that you never had. I give the Buster Cannon a 9/10 for being an all around great tool to use!