Thunder Spear

The Thunder Spears is a new technology specifically developed to fight against the Armored Titan. Referred to as "iron rods" by Eren Yeager, their official name is "Thunder Spears, due to their spear-like shape.

Mechanics
The thunder spears are  based on the technology developed by the Central police force against the Survey Corps. This technology was reused and applied to design a new special weapon against the Armored Titan. It works in a similar fashion as the Anti-Personnel Three Dimensional Maneuver Gear's guns and hooks, but with a strong spear loaded with explosives.

Usage and Limitations
The thunder spears are a weapon which enables a human team to attack together and take by surprise the Armored Titan. But it acts as a double edged sword, as it's a danger to its user as well as the Titan. So much so, that it's only useful in a specific type of situation. As such, because of the danger it poses, it should only be used when a Titan is surrounded by enough tall objects or buildings; like in a town or a forest. While it is also capable of damaging other types of Titans, its sole purpose is to kill Reiner, the Armored Titan.

Training
Squad Levi didn't have much time to train. But Hange carefully placed her troops so that they would be in an optimal position to attack. It's a maneuver that requires three successive attacks. The first to blind, the second to break the protective shell, and the third one to kill.