Place the sugar, lemon juice, and Grand Marnier in a mixing bowl. Whisk until well blended. Let sit for 15 minutes. Divide the fruit salad among 6 wide, shallow soup bowls. Ladle the Grand Marnier mixture over the fruit, and serve immediately, garnished with the mint leaves.
Place the fruit in a large mixing bowl. Sprinkle with the sugar, and toss lightly. Add the lemon juice and Grand Marnier, and toss again. Let sit for 10 to 30 minutes, either on a counter (if you like a warmer salad) or in the refrigerator (if you like a colder salad). Divide among 6 dinner plates. Garnish with mint leaves, and serve.
For the fruit: strawberries (thinly sliced the long way), raspberries (whole), watermelon (thin triangles), red cherries (pitted and cut in half), purple grapes (seeded and cut in half), plums (crescent slices), green grapes (seeded and cut in half), kiwis (peeled and sliced into thin rounds), peaches (crescent slices), nectarines (crescent slices), melons (tiny balls), bananas (thin slices), apples (crescent slices), pears (thin slices), star fruit (thin slices), pineapples