My personal favorites, homegrown here, are black diamond, and the yellow-fleshed black diamond; I’ve always found the yellow-flesh watermelons to be much better tasting in general.
My dad grew a Black Diamond once that was so big that 'area powers' packed it up and shipped it to president Truman.
As a young boy, I sat on the side of the road and sold watermellons for ten cents each, mostly Black Diamond back then.