Well, it's okay, considering that it lacks shading, or rather has shading but screws that over with double black pixels that make certain areas of the weapon look fat.
Additionally, it also looks really desaturated and flat in terms of colour - Only green red and blue? That's a very bland colour palette, especially for what should be a laser. As well as the fact that "glowing" bits don't actually glow - They look brighter, sure, that's definitely got stronger light than the rest of the weapon, but that's where the dynamic glow ends, there's not a single pixel surrounding the "light casters" that are affected by light, that should be.
Also, add some sounds - If you're going to make a weapon that sounds shoots and looks different than the default resource that you're replacing it with, you better find a good replacement for the sound not just the graphics.