You can use random(x) on a variable, and then compare that variable with a set list...
var random_item = 0;
random_item = integer(random(5)); // 5 possibilities
switch(random_item)
{
case 0 : GivePlayerAmmo(); break;
case 1 : GivePlayerArmor(); break;
case 2 : GivePlayerHealth(); break;
case 3 : GivePlayerWeapon(); break;
case 4 : GivePlayerLife(); break;
}
So you would test the random value returned and for a certain value, perform a certain task.