I cant see the image :s

I'd throw a dark band of reflection just under the big light diagonal stripe. It will make it look a bit more chromish. Dark areas directly under highlights kind of act as a hint to the eye that you're looking at something metallic. These metallic hints are hard to get right, fiddle with them a bit. Maybe look at some reference pictures of shiny objects to get a feel for how the dark blotches next to light reflections hint at metal texture.

The end of the barrel could use a bit of foreshortening along the y axis to bring it into perspective.  Same with the base of the barrel I think.

The hatch in the chest is off center, but I don't know if that is intentional.

Also he seems to gain an odd stray pixel in the mouth area when the gun fires.

The peep sight on the end might benefit from being a bit smaller and less snowflake like.

It's a good start though.

Alright!
-Rounded the beam explosion.
-Removed stray pixel.

This is something I'll need to study as I don't get it at the moment.
-moved and fixed the hatch.
-Changed the perspective for the side, tried the y axis but it didn't look right.
Before:

New version:

I thought the old cross hairs on the barrel of the gun was good.

It bothers me that the first two rings don't light up. If they're supposed to be a brace of some sort, they'd need to be a bit thicker, at least moving the shadow. Going with what TYB3N said, maybe you could also make more room for the hands.

A few other points:

• If the light is as bright as the highlight suggests, it shouldn't be affected by the shadows so much. I'd even buy it if the whole ring was the brightest green, since it's clearly casting light.
• The little dancing pixels at the bottom of the face are distracting. It could almost be a mouth doing the -.- expression, except there's two dark pixels in one frame
• If this is for a game, I think the speed is good, enough time to react, but still fast enough to be a threat. If this is just art, slow it down like TYB3N said. That lets us appreciate the the neat little animations like the sunglasses and door hatch (which could then accel/decel instead of using constant speed).