what would ye do when you run out of ammo?
fine and dandy having a massive calibre weapon, but when you've no ammunition left for it to fire, its basiclly just an expensive club that'll probably break when ye smash it over a Z's head
As for the tank, same question.. plus its a noisey bugger to boot. Starting that thing up or trying to get out of it ina safe place without being noticed by zombies would be quite hard. Imo its a noisey and perfectly safe mobile tomb.