Cut banana into fourths starting lengthwise, do not remove peel. Combine sugar and cinnamon, and sprinkle on cut sides of bananas. Let bananas sit for 5 minutes. Place bananas cut-side down on a clean grilling grate. Cook for 2-3 minutes. Using a pair of long-handled tongs or spatula, turn over and let cook 5 more minutes, or until the skin pulls away from the banana. Serve with ice cream and sprinkle with chocolate.