The 'Safe' Okay, so i got a pretty cool idea, it is when you kill a random zombie, when you are in a city, you can get a <key>. This key is a very rare drop you also need to locate where the safe is. When you have found that safe, that is in the house the zombie used to live in when it was a human. When you open the safe, if you find it , because it is pretty rarely found, since it is random and not in the same place in any other house where there's a safe in,(if there is any) there's a chance that it's nothing inside it, and there's also a chance it is a weapon safe where you can find rare weapons, but if it is something inside it you can find something very useful like anything from a can of beans to ammo to weapons, depending on the safe of course.
