A Trek around Odaiba
If you are willing to take to the road and walk the distance, I highly recommend crossing from central Tokyo into the Odaiba area. You can get there across the rainbow bridge, which will provide an excellent view of the Tokyo bay and the surrounding industrial landscape, which is actually quite beautiful.
Once you arrive in Odaiba, there are a number of interesting parks and locations to enjoy, provided you can be on your feet for a bit of walking. But personally, I feel that this is the best way to experience Tokyo.
This is a blogger who has recorded one of his own journeys from Tokyo to Odaiba, mostly on foot, and I recommend giving it a read to get an idea of what's in store!