Power outage is a bigger PITA than it is a threat to your well being.
For floods, storms, and anything that causes power outages, you want a night light/flashlight combo.
You want something like this:
http://www.amazon.com/Sylvania-Nigh...ref=sr_1_1?ie=UTF8&s=hi&qid=1284614694&sr=8-1
Place them in active areas such as stairs, hallway, bonus room, etc.
The above would be for you and/or your family's convenience. It's rather cost effective as well (anywhere from $5~$20).
For defense purposes, you want a LED with a momentary switch and preferably 60 lumens or more.
I have a Surefire 6P LED, and I find it to be a very good flashlight for the money. However, it is uncomfortable to use with certain grips.
I recommend the Z2, as it handles much nicer:
http://www.surefire.com/Z2L
But like I said, power outage is a bigger PITA than it is a threat to you.
If you don't want to shell out $60+ for a flashlight, go to your local home depot/Lowe's and pick up one of their LED flashlights. I'd get an LED maglite.
Hope that helps.