The first few times I shot the black hole gun I was scared out of my mind. That's not a bad thing, but that sound effect is terrifying!
Like Bubble said, the camera is kinda hard to use. I'm not a 3D dev, but I assume that's really hard to make. Either way, you could make it more intuitive, like having to click to move the camera so it doesn't effect your aiming and vice-versa.
Lastly, I think the black hole gun would be even cooler it it interacted with the Physics, like sucking in buildings or the cars. Right now, it just feels like a gun, but I think you could definitely make it really cool.
Overall, this game has a lot of potential, and I had fun with it. I hope this helps, and it would be neat if you checked out my submission too. Thanks!