Water. While this resource is pretty much #1 for survival, during short term power outages you will not lose your water pressure. This will only become a critical issue if electricity is lost for a significant period of time. All water municipalities have power generators for their pumps, and so long as they can get fuel for their water pumps, they can keep the water flowing. A severe enough disaster however could throw a wrench in the works. This is similar for sewage treatment. A long-term outage will prove disastrous in the water and sewer category.
Hopefully these thoughts have given you something to think about. If you are inclined to become better prepared for such things, spend a day keeping track of everything that you do and see how many of those activities involve the requirement of electricity. Then imagine life without it. Figure out ways to survive without it.