Laser is just light, why give it a dark outline?
Also, I think in your animations you try to smooth things out too much. The building up of the whole gun could perhaps be funnier if it appeared more clunky...
Same goes actually for the flash effect on his body. With a one or two frame full on flash you might achieve a better effect than this soft brightness fade..
If you don't let it loop so fast, you'll notice that the arm goes back really quickly, I guess it could stay there longer.
Why does the beam appear so softly? Make it come in with a bang! More surprising, and feels stronger! No need to draw those buildup frames.
My quick edit:
Good luck!