Crusty Gigabomb is the first ability for the Scallywag Mech. When used, the Mech will launch a massive bomb from its cannon, which will roll around shortly before detonating, much like the Chili Bean Bomb, though detonating slower.
Because this takes a while to explode, make sure that you launch this from a distance to make the explosion hit enemies. You can also throw this into gardens, eject from your mech, then fire a Gravity Grenade, which vanquishes most enemies. However, using the Explosive Escape and Gravity Grenade combo may work better.