Five Guys is known for their customizable burgers, where you can choose from a variety of toppings. However, there isn't one specific "most popular" combination as it varies depending on personal preference and location. That being said, some of the most popular topping choices at Five Guys include: - Cheese (which is free) - Grilled mushrooms - Grilled onions - Jalapeno peppers - Ketchup - Mustard - Mayonnaise - Pickles - Relish - Lettuce - Tomato - Hot Sauce So, while there isn't a single "most popular" combination, these are some of the top choices that customers often opt for when customizing their burgers at Five Guys Williamsburg location.