I buy name brand "AA" in bulk because that's the size I have in my primary gear. I keep enough "AAA" batteries to keep my small lights ready, but they don't get much actual use so I don't stock a lot. Same with "D" cells -- I keep enough to change the batteries in my 2 and 3 cell maglites (all w/ LED replacement bulbs) and that's about it. "AA" is the only size I need to stockpile for emergencies. Additionally, I bought a bunch of "AA" NiMH batteries and a solar charger -- that's a great option when you have reliable sun.