If you think that your homeowners policy covers you for everything, you might want to look carefully at your coverage. One thing that some people are shocked by is the fact that it does not cover you if your house is damaged by a flood. This kind of damage can be very costly to have to pay for out of your own pocket compared to the sometimes minimal cost of a flood insurance policy, oftentimes as low as $400 for the year. If your home is an older home or is near a major body of water, than it can certainly run you quite a bit higher than this number though.
http://www.bankrate.com/finance/insurance/survey-1-in-5-clueless-about-flood-insurance-1.aspx