First off, forget getting any electronics there cheaply unless you can't find them back home or you don't mind them being a few years old. Prices in Japan for such things are either higher or the same as they are stateside.

There are many things you can get in Japan that are illegal back home or are illegal in certain states. The best example of this would be martial arts weaponry. You can get just about anything like that in Japan but some items like extendable batons, butterfly knives and nunchaku might not be able to make it back with you.

Best thing to do is to check the prices for what you want before you leave and see if you can pick it up at a better price in Japan.

Cameras are a deal if you know what model you want, as the new models come out much earlier in Japan.I managed to save over $300 on an Olympus camera compared to here in Australia(plus a huge reduction on accessories).I own an i-Pod and a Mac, so I checked out prices in Tokyo, Osaka, Kyoto in some places they were the same as here in OZ but some stores would offer you a final price that would surprise you.You need to do a lot of footwork to cover all stores and get business cards with the price and model written on the back.Then you can get someone to help with japanese at say your hostel.My camera price was reduced by a very helpful receptionist at a hotel,she rang a store for me , explained what I wanted( a particular camera with lens and a few accessories ) and came back with a better price than what I could find.