Prepare the Dry Ingredients. In a large bowl, combine finely crushed vanilla wafer cookies, cocoa powder, powdered sugar, and chopped nuts. Stir until well blended.
Add the Wet Ingredients. Pour in the dark rum and corn syrup. Mix until the ingredients come together to form a thick, sticky dough.
Shape the Balls. Using your hands or a small cookie scoop, form the mixture into 1-inch balls.
Roll in Coating. Roll each ball in your preferred coating—powdered sugar, sprinkles, or shredded coconut. Place them on a parchment-lined tray.
Chill. Refrigerate the Rum Balls for at least 2 hours to allow the flavors to meld and the texture to firm up.