I may be swimming upstream a bit here, but I see the total collapse as the least likely in terms of we may very well get there, but not in 24 hours.

Even taking one of the total collapse scenarios - financial system: What would happen if by the end of today, the Dow Jones was at 0 and major banks collapsed?

If you are even semi- prepared, nothing. There will be a run on the banks if they are open, but we don't have much if any cash there anyway. There will be panic buying, but we are already stocked - need to top off the gas tank, and prepare for bug out.

The reaction over start to day 3, day 7, day 15, and day 30 is more interesting. By day 3, it becomes obvious that the FDIC is unable to keep the banks operating and the FED can't deliver enough cash to meet withdrawl demands, despite government assurances that your money is safe. Then the panic buying sets in and store shelves are empty by day 7. By day 15 people are not getting paid, can't cash or get to payroll deposits (those that forgot to cancel direct deposit), and ATMs, credit cards, etc. become useless. By day 30, the financial system has imploded, as the means to pay bills (telephone, electric, and such) or get funds has ceased to function, and emergency measures fail.

Only, under the most extraordinary circumstances would we not have 24 to 72 hours to react. It does not mean that cities are without water and electric the same day ....