Besides my computer, the power tools I use in my shop and the coffee maker, the battery charger I use for my camera batteries is my most used device.
I can't imagine buying disposible batteries, especially with all the pictures I take (and retake) of my work, flowers, creatures, the world around me, etc.
It really bummed me out last year when my sister in law came to visit and actually bought batteries for her camera, she says she doesn't bother to use rechargable batteries they are too much of a PITA. I was so surprised and shocked at the amount of batteries she must go through. More hazardous crap in the landfill. Even when we travel, which hasn't happened in awhile, I would always bring my recharger with me. I'd like to get an additional set of 4 soon. Too many times the lighting would be right for a reshoot but the batteries needed rejuicing. Or, a bird would be close enough to have its picture taken, but I just didn't have the power.