AMMO
The great thing about having a weapons system in the game is an ammunition mechanic. Notice that each of the weapons I listed has a Type. This ties directly into ammunition. The map could be scattered with Ammo objects (face down). When you step on one you get to flip it up and see what kind of ammo it is. So if you're holding a pistol and find some shotgun ammo, then you're out of luck unless you want to give it to a teammate who has the correct weapon (as a free action). Ammo can even be random:

When you turn over an ammo object, roll 1 die. This is the total amount of ammunition you receive.

Imagine running out of shotgun shells, and stumbling onto a box of 4 shells! Watch out!

SUPER MONSTERS
Left 4 Dead and Resident Evil took the Zombie Apocalypse concept one step farther by adding Super Monsters! These creatures often have more life, some sort of damage reduction, and a nasty special power.

• Left 4 Dead Hunter: Give this monster a power action and make a ranged attack as if it has a range of 6 against a single survivor. On a successful attack no damage is deal; instead, move that survivor next to the Hunter.

The Hunter's a nasty piece of work that uses it's tongue to capture survivors and drag them closer. *shiver*

There's lots of different possibilities for a Zombie Apocalypse miniatures game. We at HeroClix World hope to see one soon!