Steak 'n Shake's "Side by Side Milkshakes" stood out against the competition not because of the individual flavors out of which they consisted of, but because of how the restaurant combined those flavors together, As the name hints, the Side by Side Milkshakes were split down the middle with two standard shake flavors rather than blended together.

Steak 'n Shake used to offer four flavors of its Side by Side Milkshakes -- Strawnana, Banocolate, Strawnilla, and Vanocolate, which all consisted of either vanilla, chocolate, strawberry, or banana flavored shakes split with another one of the three flavors. 

It would be pretty cool if Steak 'n Shake brought back the side by sides and allowed for more customization options for the customers.