Big box stores are Yodobashi Camera, Bic Camera, Sakuraya, etc. They don't discount off MSRP, instead they give discounts in store points applicable toward future purchases. Every item carries a 3% 5% or even 10% of its price in points rebates. Signing up for a point card for a foreigner may be a challenge though.

Temporary visitors can claim consumption tax exemption at the time of purchase. Ask for Menzei. Once I saved my friend about 1manen on a laptop at Tsukumo in Akiba.

Kansai people will claim Osaka's Nihonbashi dendentown is just as good if not better than Akihabara.