Everyone knows about Japan's watermelons shaped like hearts, cubes, the Great Pyramid of Giza and all sorts of other things. That doesn't make them any less impressive in person. Go ahead and gawk.
There are always a few at two spots in Tokyo Station, both accessible from the basement level Yaesu central exit. As you're exiting the turnstiles, take the hallway to the left to a fruit shop on the left side across from Character Street. Or from the turnstiles, go straight past the Glico snack store and find Daimaru's depachika, which has a fancy fruit section.