Particle Beam Cannon

[Crow]

First thing is, you shouldnt save as jpeg. Png or gif is the only way you should go when saving such things. Second thing, it looks like some "filters" or other things were used, but that may be the jpeg artifacts, too.
The whole gun design looks a little weird, since the front of it seems to be heavier. Also, the whole thing is pretty dark, you can hardly see anything. You should add some contrast, and maybe also an outline.

[Kirble]

I have a nicer bullet graphic. Make it like smoke wisps intertwining, i'll try and draw one up, and have energy balls around the wisps.