The loser with a known phobia of heights does the thing: skydive, bungee jump, zipline, or ride the giant drop tower, filmed from takeoff to landing. Only works with genuine but safe commercial thrills, never improvised danger. The scream audio becomes the league's ringtone.
Heavy sentence
Severity 4 punishments are the ones people talk about for years, which is exactly why they need full league buy-in before week one. Put it in the constitution, set the deadline, and agree on proof requirements up front.
Budget note: this is one of the expensive ones. Decide before the season whether the loser pays, the pot pays, or the league splits it, and write that down. Money arguments kill leagues faster than collusion.
Seen in the wild: fantasyfootballunlimited.com