That is a pretty vague statement...world ending? But lets say I was either the last man on Earth...or one of the last several thousand on earth...Seriously I would most likely head to my safe as it has firearms, ammunition, cash, and even some gold. From that point I would head to a Wal-Mart and try to take it over...I read some would loot a Wal-mart...I would prefer to live in the Wal-mart...possible use the already supplied gates to keep looters out...or...that is what the firearms would be for I guess. It sucks in a time of tragedy to think of resorting that way ... I would try and reason to any looters but if it got to hostile I would do whatever it would take to secure my find. I would use the roof as my garden to grow my fresh vegetables ... and anything that might have a short growth period. I'd probably eventually use my cash, gold or food rations to send people to get me lumber to better block off the entrances to the Wal-Mart. I'd also use the roof to hunt down meat...birds, rats, ect and ride it out till civilization kicked back in.