It is considered to be most durable and easy to access equipment device. (aimworkout.com)
X allows you to access the equipment screen, A is used for jumping and B is your go to button to fire any and all weapon you collect throughout the game. (miketendo64.com)
These are limited use items, which can be changed by accessing the equipment menu, and you'll pick up more as you run around the stages. (plusxp.com)