友達やMrs. Frogの親戚などを東京・関西ガイドするのが多いので有名地ならマスターしましたが
ナイトライフは東京もNYCもPhillyも全然知りませんー。
(ナイトライフと言えば自宅でゲームとか、残業とか)
横浜は大学時代のルームメイトが大地主の跡継ぎさんなので、よく行きます。
高島台とか、家名が駅名だったり。

I end up guiding my friends and relatives in Tokyo and Kansai so I have the touristy stuff down, but I no nothing about nightlife anywhere
(My only nightlife is gaming at home or overtime at work)
I often go to Yokohama since my college roommate is a son of the prominent  and ancient landlord there; a station is even named after his family name.

If you're taking a day trip from Tokyo, an organized tour to Kamakura (old capital) or Nikko (temples, water fall, ninja town, hot springs) would be the touristy thing to do.  Or you can hop down to Yokohama (around 15-40 min from Tokyo depending on where in Tokyo you start from) and see the harbor, old city, and chinatown for half a day.  If you want the hot spring and ocean experience, Izu and Atami are great.  Off-season prices aren't too bad, but you might want a car rental there if you want to get around.

If you want to take the bullet-train shinkansen, a kansai day-trip to Kyoto (old capital), and Osaka (second biggest city) is manageable but a little tough and wasting travel time.  It takes around 3 - 5 hours depending on the train class.  Staying a night there is recommended.  Nagoya is right in the middle of Tokyo and Kyoto/Osaka so a day trip is manageable, and it's the 3rd largest metropolice area in Japan.  It's relatively new so there's not much historical stuff there, though -- save a reconstructed castle.  If you can spend a few days, an organized tour of Kyoto, Nara (even older capital but best UNESCO historical sites), and Osaka / Kobe (not much there...) in Kansai would be great.

Otherwise there's plenty of stuff to do in Tokyo which isn't part of normal tours:

• Check out weird dressed people in Yoyogi Park entrance in Harajuku. (sample video)
• Wander around Kabukicho redlight district in Shibuya. (it's safe, with police head-quarter right in the middle of it)  Be sure to visit the Hanazono Shrine, one of the fox "Inari" shrines in Japan. Also climb the Tokyo Capitol building to the observation deck. (free)
• Wander around the Radio-Kaikan (link is PG-13) in Akihabara and buy cheap Pangya figures (like this). Also check out the maid cafes, butler cafes, cross-dresser maid cafes, etc.
• Take the robotic train Yurikamome to Odaiba and spend some time in the theme parks in Odaiba.  Probably not that fun alone, but the cyber amusement park Joypolis by Sega is pretty fun.  There's also a hot spring facility. If you don't want to go all the way to Atami / Izu but want to experience the onsen.  (You don't need to stay)
• Go to Roppongi Hills and marvel at the rich people or shop brand stuff.  I guess it's usually part of Asian tours but not American ones.
• Check out Otome Road in Ikebukuro, the girls version of Akihabara. (although tiny)  You can check out the aquarium in Sunshine 60, too.

i have been to tokyo many times with tour groups before and been to most of those places. but this time im going by myself and i want to look for interesting stuff. i might take the high speed train to other cities also.