Japan has begun marketing watermelons that are about one foot square. They are shipped in a square box with no padding, taste like a normal watermelon and cost around $80.

A square watermelon is made by inserting a young Japanese watermelon into a tempered glass case while it's still on the vine.
These are the only reasons I could come up with for making a square watermelon:

1. Easy to store
2. Easier to cut up
3. Won't roll away
4. Because it can be done
5. To sell to Americans

Source: The Daily Show with Jon Stewart and Chattering Magpie
not slashdot