Cool effort! I liked a lot of what you did with this one.
For one, I thought the writing was funny. The walk animations were so hilariously bad (this was intentional, right? hah). Give your composer a pat on the back, the music is very solid. I really like the main menu theme especially.
My biggest issue is that I wish there was a little more hit feedback/ways to avoid damage (like maybe if the enemy bullets were slower?) The turret was the worst offender. The sound effect the turret makes when it is firing is not at all obvious, and I would find my health would just be silently dropping. You could do the classic red screen and SFX hit direction indicator or something.
I agree with the other commenter that the railgun seemed strictly worse than the pistol. If the pistol wasn't so good, this game would be hard to play. Fortunately you can snipe from two football fields away with that baby.