What is the best weapon during a zombie apocalypse?

Now, before you answer, I do not want to hear about what is your favourite weapon, or a half cocked gut feeling about what you believe is the best weapon.
I want you to evaluate the options based on durability, long term usefulness in the face of resource scarcity, effectiveness in various circumstances, like close quarters, rain, massive crowds of zombies, etc. and drawbacks that each weapon has.