Once the "hook" zombies arrive in melee you cannot hit them anymore.
Only 1 "skin" for each type.
Five bullets clip? Ridiculous.
Crosshair useless, no zoom and not even "shrinking" while you take the aim.
Man, this game is no good.
Don't play it.

Why are the zombies BLACK?

Bullets go straight through the zombies ... imagining you would actually be able to shoot the zombies it would still be a dull game

Not a bad game. Graphics are decent and playing it is simple and kinda fun...
That being said, there are several things that should be addressed:
1. Tell the player outright that you can switch weapons with 1, 2, and 3.
2. Note the spacebar zooms.
3. The graphics are in need of repair: some of the closer enemies are smaller than farther away ones. now, if this is intentional, take it out.
4. Lower sensitivity on the mouse. It was a hassle trying to get a perfect head shot each time with such a troublesome control.
5. Addressing part of previous statement: make it so that you can kill the zombies with something other then a perfect head shout each time. While it makes some sense, it is too difficult with the sniper rifle. I let them all start getting close and just using the more useful pistol, which is something i would rather not do seeing as the game is called zombie sniper.
6. Finally: please add some upgrades or bonuses like grenades or something.

Its a good game but it need more option like new guns and upgrade