I think without context it looks puzzling. Add character and fire to suggest that it is really a gun. And outline on the left is choppy. See 'clean lines' here:

http://www.pixeljoint.com/forum/forum_posts.asp?TID=5692&PID=96434

http://zachattackinc.com/portal%20gun.JPG thats where i took inspiration from

 The shape looks alright - however, there's some spots like the back of the gun which could work with some aliasing. Like vampireslug mentioned, some parts look a bit JPG-y, too.

I'm not sure about this one... I like the subject but the piece itself looks more than a little JPG-ish, there are a lot of colors that I'm really not all that sure were placed on purpose.  I could be, and hope I am, wrong. 

well, even knowing how the portal gun is made, I should admit that a little bit of AA could help improving the overall look.

You really have to know what the "Portal Gun" is and how it looks to understand what this is.

This image is somewhat unclear.  Its hard to tell where the gun begins or ends.  Maybe it's because the sprite is out of context... dunno