Shoulder

The shoulder is the most vital component of a Transformer's body.

It is unknown why the shoulder is such an achilles heel of Cybertronians. However, it is clearly the most easily damaged location on their chassis, as many instances of minor damage have led to grave injury and even death.

Such instances include


 * In a battle on Earth, Ironhide was shot in his shoulder by Megatron. Seeing this injury, Optimus Prime immediately called off the attack to get Ironhide immediate medical attention.
 * Years later, the incredibly strong Autobot Brawn was killed in a single blow from a wound to the shoulder.
 * Shortly afterwards, Ultra Magnus was rended into five pieces by an attack by the Sweeps. However, he was in a state of near death until he was repaired, unlike Optimus Prime who had been torn into pieces one before.  Presumebly, the Sweeps had damaged his shoulder, wheras Prime's was treated with care.

There are very likely many more examples of Shoulder wounds and their fatal nature. The only theory is that many Transformers store their Spark in their shoulders.