Everyone needs batteries, but people with families (and especially toys and games) can burn through batteries pretty quickly.  We were using a bunch of Duracell batteries that we would buy at Costco pretty frequently, but the cost added up, and also we felt that all this battery waste was not good for the environment.

We bought a Duracell Rechargeable AA 4-pack and charger and from Costco, which works pretty well.  This is sold by many retailers including Best Buy and others.  Also, Energizer makes one too, which we have not tried, but it probably is just as good.

Important Note: Some electronic devices such as Leapsters might not do well with these rechargeables.  I think this is because for some reason the rechargeables are 1.2 Volts whereas regular batteries are 1.5 Volts.  We tried them in the Leapster and the work most of the time, but occasionally don't work well.  These are probably best for simpler devices and toys like kids flashlights or motorized cars rather that complex electronics.