Lightly oil the halloumi sticks and grill them in a heated BBQ at medium heat (covering the grid with a non-stick BBQ cooking mat is ideal to prevent the cheese from sticking to the grid). Grill on each side. Cut the sticks into coarse cubes.
Divide the melon and cheese cubes in a serving dish and drizzle with the vinaigrette.
Garnish with roasted pumpkin seeds, tarragon and chives. Salt and pepper. Serve immediately.