Lightning Gun
A "Lightning Gun" is the standard and distinctive weapon used by Macbeth. It was named only once, in the episode "Pendragon", when King Arthur referred to as a "Lightning Weapon". The device has yet to be given a more "technical" name.
Characteristics
A "Lightning Gun" is an electromagnetic weapon with two electrodes that generate the charge. Macbeth uses it as his standard weapon, as did Banquo and Fleance when they were still under Macbeth's employ. Griff also appropriated one when he fought Macbeth and his stooges.
Xanatos' "Macbeth Robot" also used a "Lightning Gun", but he has not made use of the weapon elsewhere.