1/2 oz Lime juice
1/2 oz Grapefruit juice
1/2 oz Orange juice
1/4 oz Sugar syrup
3/4 oz Gold Puerto Rican rum
3/4 oz Martinique rum
2 One inch chunks of pineapple
1 Dash of Angustura bitters
1 Dash of Orgeat syrup

This drink from 1955 is one of my favorites.
Mix everything in a blender until pineapple is liquefied. Shake the juice in a shaker half filled with ice cubes. Pour into a hollowed pineapple.