If I wanted to use nimh AA batteries in a flashlight, which one should I look at?
MagLite LED?
Another?
Features need to be :
Rugged (atv use)
Budget (I can't afford an expensive light)
Brightness
The MiniMag LED is not that bright compared to many of the better brands. You get what you pay for applies to flashlights. Up here in Canada the MiniMag LED sells for $25 and a better flashlight costs twice as much or more. However, the more expensive lights have much better light output, better beams (spot and spill), and better runtimes. For instance, the Quark AAx2 has twice the light output in High mode and runs for 5 hours compared to the Mini which runs for 3 hours. Mag has a newer version which uses the Rebel emitter which is a bit brighter and runs a bit longer, but it still doesn't match a good flashlight for output and runtime as they have been updated with newer emitters that are brighter and more efficient too.
If you need a lot more output, lights like the Quark can run in Max output mode which gives it 5x the light output compared to the MiniMag at the expense of shorter runtime of about an hour. I'm biased toward the Quark line since I own one, but it's an excellent light and comes with lots of goodies like a holster, lanyard, handgrip, and even shipping and taxes all included in the price. Other brands can be found for less at the expense of features and/or performance, but there are lots of lights out there and I'm sure you can find one that meets your price range and performs well.
Maybe check out some of the AA reviews and see what's available. Several months ago I would never have thought about replacing my MiniMag LED or my big MagLED 3D light, but the small Quark AAx2 has replaced BOTH lights. Given that the two Mags cost me the same as the Quark, it only makes sense to spend more and get a better light.
Good luck!