Sunrise on the New Year's Morning
You will only get one chance a year at this, but if you happen to be in Japan during the new year, you can see literally the first sunrise on earth. Many people will either stay up all night or wake up especially early to see the first sun in "the land of the rising sun" no less.
However, even if you aren't here in Japan at the start of the new year, the Tama river running along the Tokyo southern border is an amazing place to see a sunrise. The pink and orange hues split with the yellow sun reflect over the water in front of you, and the solemn buildings in the distance. As a bonus, if you go for a winter sunrise, you can usually see Mt. Fuji from the Tama river, although it will be very cold, so be sure to bring some gloves.