1. Wrap each cantaloupe cube and each honeydew cube with 1/2 prosciutto slice. Thread 1 wrapped cantaloupe cube and 1 wrapped honeydew cube onto each of 16 (4-inch) skewers. Arrange skewers on a serving platter.
2. Combine juice, oil, and pepper, stirring with a whisk; drizzle evenly over skewers. Sprinkle evenly with mint.