Have been coming here for ages. It's changed quite a bit over the years, but is now a pretty good place that has a variety of shops. If you're in need of authentic Japanese stuff (mainly good), Japan Town is where to go.
Heisei - The prices seem a little higher than necessary. I recently came back from a long term stay in Japan where I went to the grocery store often and noticed the very significant differences in price.
FaMu - Shop here for some great meats. They also have their items packaged, which come in handy on those nights that you don't feel like cooking. FaMu also serves daily lunch specials.
¥100 Shop - A lot of good finds here. I often buy their clear plastic folders for work. Their Tupperware comes in handy as well.
I could go on, but these three shops are where I go to the most.
Good for: Japanese goods