Sometime since I was out there, but definitely Akihabara in Japan.
Big shops, small family stores sell everything and anything electronic.
Can be a little intimidating for the tourist (langage problem, everything printed in Japanese, obviously). Didn't buy anything there, but great for checking out the latest in techno stuff.
More tourist-friendly is Hong Kong (Nathan Road). At least I could bargain in Engrish
. Got a nice Olympus camera and Seiko watch there for a great price, but probably cheaper now online, as my trips were before online shopping took off in a big way.
Llew