A cannon that fires bombs. Bombs are not used on their own.
Holding the button locks Link's movement, and arrow keys affect his direction. Releasing the button without charging the cannon will plop a bomb out right in front of you. Holding the R button (or equivalent) while the cannon button is held down will charge the cannon. When released it will shoot a bomb a distance directly proportional to how long you charge for. The bomb shoots out and will either land and spark before exploding or it will explode on impact. Along with the item, you gain the ability to carry bombs.