Currently, there are only 3 Shock Weapons in the game, making this damage type very unique.
They are the:
Trailblazer, a pistol modeled after a 19th century Revolver (aka. 6 shooter). This weapon is manufactured by Smoke Stack. This has high damage for a pistol, but a tiny capacity of 6.
CM Gigavolt, a full auto (albeit relatively slow firing) assault rifle created by Critical Mass. Many consider this to be the best of the 3 Shock Weapons.
CM 800 Jupiter, a semi-auto sniper rifle also made by Critical Mass.
Shock weapons use millions of volts of electricity to damage enemies. In addition, the electric will arc and hit other targets around the target initially struck. Enlarged increases the arching range of the Shock, allowing it to reach out and shock targets further away from the shooter. Piercing increases the number of secondary targets the shock can hit. While the damage of the Shock Weapons seems low, they have an ace up their sleeve. One unique thing about the damage dealt by shock weapons is that it's multiplied by the number of targets Shocked. For example, if your Shock Weapon hit 4 targets at one (including the one hit initially), than the damage dealt to the zombies involved in the Shock is multiplied by 4. This makes it powerful on large crowds, and makes piercing an essential augment on Shock Weapons. Recommended augments for the Trailblazer include Deadly, Piercing, and Race Modded/Capacity. Every Gigavolt should have Deadly, Piercing, Overclocked, and Adaptive. The Jupiter should have Deadly, Adaptive, and Piercing.