Batteries! The ugly side of portable consumer electronics... I usually just use NiMH rechargeables, but you can't really argue with this:
32 AA batteries from a single 6v.
In a similar manner, one can also remove 6 AAAA (yes AAAA) from a single 9v.
Or 8 watch batteries from a 12v.
links courtesy of lifehacker.com
Have a good weekend!