Melon seeds are the seeds of a watermelon-like plant. The fruit has been removed during processing. The black melon seeds we see are actually seeds.

Sunflower seed, if it is shelled, is a fruit. Plants are morphologically called achenes. If you peel off the shell and leave the sunflower seed kernel, it is a seed.

Peanut kernels are seeds, and only peanuts with shells can become fruits. Peanut is a leguminous plant and a pod.

A corn kernel is a fruit. Its pericarp and seed coat are closely combined and belong to caryopsis.