Awesome thread! Here is what I have
-Whole house generator running on natural gas (if you can’t justify the expense, a battery powered air pump can suffice on a $50 battery backup can run for 4-5 days)
-$100 Window AC in case of lost AC unit
-Dual return pumps (highly recommend)
-Declorinator (highly recommend) so I can use tap water in case of emergency and no less then enough salt for 100% water change (all city tap water is just fine for water change. If you have a well then that may be not be safe)