The league selects an iconic, preferably emotional, movie scene, and the loser reenacts it in public or on video with full commitment: the Titanic bow, the Dirty Dancing lift, the Platoon knees-drop. Posted to their real accounts. Oscar clips only.
Budget note: this one costs nothing but dignity, which makes it a strong pick for leagues that would rather spend the pot on the champion than on the loser's downfall.
Seen in the wild: fantasypunishments.com