The Thundergun is a cannon-shaped weapon that fires directional blasts of incredibly strong wind. It has no iron sights. It appears to be able to kill large numbers of zombies with a single shot, sending them flying backwards or up. Those who are not killed by the wind blast are thrown backwards and will remain on the ground for a few seconds before getting back up. The Thundergun holds two rounds in a magazine, holds twelve reserve rounds and can only be reloaded when all shots have been fired. When Pack-a-Punched it becomes the "Zeus Cannon", it has an increased magazine size of 4 and carries 24 reserve rounds. It has increased range and radius, and can now knock over and slightly damage zombies off screen. The Thundergun is most important during the later rounds as it is useful for clearing large groups of zombies in order to reach a downed teammate or make an escape. It is extremely useful when swarmed because it will easily kill a large group of zombies in one shot.
It appears that the Thundergun (DG3) and the Wunderwaffe DG2 are both meant for taking out large groups of enemys just in different ways.
When Richtofen recieves this from the Mystery box he sometimes may say "Could it be? DG3!"
When Pack-A-Punched, this and the Olympia's names refer to Greek Gods.