Akasaka (sp?) is fun too. Its the 'night district'.

The first time I went to Tokyo, I actually had a day off (completely surprising). I spent that day on a bus tour of Tokyo. That tour covered everything. We went to the moat surrounding the palace (which is right across from our hotel, so I saw it before), the WTC, and the oldest temple in Tokyo, among other attractions. Its the best way to see the city IMHO.