In Monopoly, each player rolls 2 dice every turn to determine how to move game pieces forward on a board consisting of 40 squares. Many different versions of the game exist all over the world, and various actions are required whenever the player lands on the “Free Parking” (square 21).
A suggestion is that when that happens, the player should be allowed to roll inverted for 3 turns (or maybe until the player lands on “Jail”). An inverted dice roll with 2 dice has 11 different outcomes (from 10 to 20), whereas a normal roll with 2 dice has 11 different outcomes (from 2 to 12). This could give the player a significant advantage for a limited number of turns.
I tried that with some friends. We decided that the player had to choose whether to interpret the result inverted or not BEFORE rolling. Whenever somebody landed on 21 they got this opportunity for 5 rounds. It worked fine.