Famous for its electronics, new and used, Akihabara is a very intense couple of blocks. Packed with surprising numbers of cheap restaurants (why didn't someone tell me this beforehand!??!?) that smelled delicious, maid cafes, tons of old and new electronics, plus a few food trucks and of course, Yodobashi Camera's massive location. Super Potato for old school console games (thanks for pointing this out, James!) is pretty damned cool, too.
The Shinjuku location of many stores is now rivaling other areas, and the Bic Electronics is honestly almost as good as Yodobashi-Akiba. It's still worth a wander though, as the first floor's Apple sales effort is enormous.
South to Chiyoda, Tokyo Station's new brick facade (very quaint), and then the Imperial Palace East Garden, which is the only area open without an organized tour. Kind of like the Meiji Jingu shrine in how reserved it is, but with large low-slung walls and guardhouses. Probably missed out on quite a bit without a tour, but that had to do.
Wandering the office towers with built-in multi-level malls and food courts west of Tokyo Station was kind of neat. Shin-Marunouchi and Marunouchi buildings are just two of many large buildings with setups like this. Issa-an for some of the best tempura soba I'd had (crab claw tempura!), then finding out how truly massive Tokyo Station is as I wandered through the north and then east ends through Kitchen Street to Ramen Street. Holy crap, it is big. I thought I'd found ramen at Kitchen Street, didn't see much ramen, was frustrated, kept walking, saw another area, kept walking, and walking... and finally found it. Crazy.