Beside the tremendous amount of selection, Akihabara has those unique items.

I bought a CF card to 2.5 inch ATA adapter on the backstreet and made my our SSD notebook PC. I bought a single bank 512MB SDRAM DIMM there for my Minolta color printer. Many places wouldn't even know the difference between single bank and dual bank.

For highend camera stuff, Yodobashi in Shinjuku and Bic Camera in Yurakucho are still better.