It was a decent Shooting experience. And it surprised me that you managed to pull of a 3-D shooter with only using Flash! In any case, the only problem your game lacked was immersion. For one, the player's enemies didn't respond to you shooting them well, i.e. they simply stood still as you kept shooting them unless you are in their point of view.
The fact that you didn't give the players more "lives" so to speak shows that you decided to use a traditional arcade platform, which is a game that is incredibly hard to beat. This was used back in the days to make people pay more money if they want to beat the game. However, keep in mind of your target audience, i.e. Newgrounders, a group of people whom are bored and want to look for some fun games/movies to pass the time.
Finally, the controls where kinda boggy as it wasn't sensitive enough for my tastes. If you want to release another first-person shooter, I'd recommend looking into adding an option menu with the ability to change the sensitivity.
However, all that said, you've done a decent job. The textures of the backgrounds and characters are decent (considering that it's flash) and the sounds are alright.
I'd give it a 3/5...
Decent effort