If you have a time, try going to Okachimae for anything goes shopping. Many food items and very good prices. There are lots of yelling to get customers's attention. Close to Ueno. That is where many Japanese go to do New Year's Day cooking shopping for many traditional things.
kyoto also has one similar but smaller and higher prices.
spend a day wandering around Tokyo Station inside. It is endless stores and restaurants and PEOPLE!
to me, Shinjuku is getting seedier and becoing a magnet for younger generation, school break etc. check out Ebisu area.
Fun shopping for household items are at Tokyo Hand. You will find them in various locations. You will hit cherry blossom season, but stay away from Harajuku. Too crazy packed. Instead head down to Meguro station or Gotanda and head toward Meguro River. Much less crowd and cherry trees by the river all along.