Goron Missile is a glitch that lets you gain incredible speed as Goron using wither the hookshot or the bow
Due to how MM3D interprets holding down on the circle pad, it's easier to get a consistent direction for a Goron Missile by facing away from where you want to go and holding down when rolling.
The speed you get will depend on how much you hold the circle pad in any direction. Let's say you hold up just a little bit, the speed you will get is going to be different than if you held the circle all the way up.
For reference, backwalking speed is 16; you can easily reach a speed of 1000 doing this glitch.
If you do a pound on slopes and other tilted surfaces you shoot up vertically