Positron

Positrons are a particle which make up a the spark of a Transformer.

Beast Machines
While being menaced by a strange entinty composed of electrons, Rattrap wished that he had a source of positrons to neutralize the entity. This train of thought led him to realize that the entity was a depolarized Transformer spark. Using a spark extractor, Rattrap managed to restore positrons to the entity and bond it to a single body. However, what he probably didn't expect was who it would turn out to be&mdash;Megatron.