CLOWN ZOMBIES!
I -loved- the clown.
Ok, now on to the review.
This is damn impressive for a first game. The intro / menu screen was professional looking and the weapon sounds were great. The weapon firing animations were good, but some of the zombies were a bit goofy. For instance, the way the soldiers fell was a bit cardboard cut-out like.
Suggestions:
Weapons - what, no home-made flamethrower? Aww :( Seriously, I think some improvised weapons would add realism. Molitov coctails (limited ammo for these!) would be good. Perhaps you could add the risk of damage to the barrier if you used one too close.
If you started out with nothing but a cleaver and a pitchfork, I for one would love it.
Ammunition - Rather than only getting the choice of two weapons for the night, what if you had all the weapons available, but limited ammo for each? It would add another layer of skill to the game. (You might also want to add "search for ammunition" as a daytime task)
Daytime hours - Do they not sleep? You could add fatigue as a factor. The less rest you get, the less accurate you are with weapons.
Survivors - Damn, only one woman? I hope she idolized Smurfette as a child.
Story - This may not be your thing, but I always like the adition of a story, a bit of narration can add to the realism and excitement of a game.
Great job, overall :)