"Fires a continuous, directed beam of ionized particles."
The Ion Beam fires a red, straight-line, long-range laser. This weapon can be fired continuously by holding the button down. It can be fired in all 8 directions. It looks a lot like the beam weapon fired from a Laser Urchin.
When Trace aims upwards and fires the Ion Beam while walking, he can easily lure out and kill flying enemies that are off screen.