How do you create an explosion? GIMP?

I would like to create an explosion and a different looking laser beam effects for a test blender game I’m working on. I believe I would use GIMP for this so I posted this here. How do I do it?

Btw, the explosion doesn’t have to look like fire and smoke, it can be some sort of energy explosion, or whatever. What I want to do is make as many explosions and beam effects as possible, all with different looks (a certain explosion for a certain beam). So just reply with whatever ideas you have or tutorials I can use to do this.

Many thanks in advance!
Myles