The loser catches a live fish and puts it in their waistband for ten seconds while the league counts down in unison. It is exactly as stupid as it sounds, and one league swears it transformed their competitiveness overnight. Catch-and-release rules apply to the fish, who is the real victim.
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.