Plasma

Plasma is a highly ionized gas that's not fire, electricity, light, darkness, explosion, spirit, telekinesis, illusion, life, death, magic, or ki. It appears in the Mega Man franchise.

Description
Plasma is the foruth state of matter. It is present in electricity, extremely hot flames and polar Aurora, or artificially in low energy lights, electric arcs of all kinds, etc.

Story
In the Mega Man franchise, plasma is fired from various busters. It is also used by various enemies (such as Mets) and bosses as well.

Trivia

 * Plasma has a similar appearance to ki.