Problem With Ammo Pickup

[system]

What script would you use to: run into a crate, destroy the crate when you run into it, not let you shoot unless you have more than zero ammo and add ammo to your inventory.

[Meater6]

The crate part I think I understand how to solve. Try this:

//OnCollisionEnter detects if something has touched the object this is on
//OnTriggerEnter can be used for trigger colliders
function OnCollisionEnter (object : Collision) {
    //the crate needs the Crate tag
    if(object.tag == "Crate"){
        //destroy the crate
    }
}

The ammo part is just simple math, so I kind of don't see the problem. It should look something like this:

if(fires){
    if(ammo > 0){
        ammo--;
    }
    else{
        print("NO AMMO");
    }
}

And please, look at the FAQ guidelines for better question asking, it will get you better answers.