Sheesh.
Okay, for those who don't know any better: (Those who do, just ignore me.)
Rechargeables for high-drain devices.
Ni-Cd used to be the rechargeable for things like RC cars and such that drained the battery completely each time.
Now that Ni-MH has higher capacities, I can't think of any reason NOT to use Ni-MH for any and all high-drain toys. Not only can you get a higher amp-hour in the same physical size, Ni-MH batteries don't have (toxic) cadmium in them when they've reached the end of their life.
Digital cameras and cordless phones are the perfect applications for Ni-MH batteries. You almost never want to get to a no power condition before you recharge.
Li-Ion batteries are better than Ni-MH, but much more expensive and limited to custom applications. (If someone knows of readily available AAA, AA, C and D Li-Ion, let us know.)
Alkalines for slow drain devices like clocks, remotes and ESPECIALLY smoke detectors. Don't ever use a rechargeable in a smoke detector. The battery will self-discharge before the detector uses the power. Lithium batteries can be used in place of alkalines, but they're VERY expensive. Smoke detectors are about the only place that Lithium batteries make sense.
So, for the threadcrappers, there will always be a need for a good price on alkaline batteries. (Until they make a reasonably-priced rechargeable that won't self-discharge.)
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