I carry one that doubles as a defensive weapon in the event things go bad when I'm in the back.
The plastic-case units don't have enough mass to be effective in striking someone and rendering them dead or unconcious. IMO, the 3 cell Maglite works very well. It can be safely modified with a strap so that if used as a weapon it will remain secured to the user. It also has a bright halogen bulb for when being used as a light.
I stick with the heavier disposable batteries as the lighter rechargable units reduce the overall mass of the flashlight, but that's just personal preference. In the event I use it to strike someone I like it to be slightly heavier.
Times have changed. Think dual-use.