Level 1: Beam Sword
Level 2: Hyper Bazooka
Level 3: Hyper Hammer (fly on Goufs and hit their target spot.: It destroys them in one hit.)
Level 4: Beam Rifle, Hyper Bazooka
Level 5: Beam Rifle (you have no choice)
Level 6: Beam Rifle (same as Level 5)
Level 7: Beam Rifle (fighting in the forest) or Hyper Bazooka (fighting in open range)
Level 8: Beam Rifle
Level 9: Hyper Bazooka (for most ammo) or Hyper Hammer (for power)