Killer Bean Cheap Effect Pistol Fire

This is a very simple muzzle flare that works, as explained by Jeff Lew.

The shape that comes out of the gun ... it is flat, so you have to control your camera angle:

 

Alternate: you can also clone an instance at 90 degrees along X.

The material: bright yellow, self-illuminated ...

 

Scale from about 1% to 100% repeatedly, up and down every few frames:

Add glow in the Mat ID:

Just use source color and make it intense enough: