The party were fighting a sorcerer, and were all too close for the party's wizard to risk casting most of his spells (most of them are attack spells, and with so many people in melee, he's risk hitting one of the other party members). However, he did have some cantrips available, specifically, Shadow Bite.
The wizard cast the Shadow Bite on the sorcerer. On a failed Fort save, it forces a Concentration check if the target is casting a spell (he wasn't), 50% chance to make them drop anything they were holding (empty handed), and makes them fall prone if standing, or stand if prone.
I knew there was next to no chance of success, with the sorcerer's Fortitude save, and the low save DC of the cantrip, he'd only fail on a one, but the wizard went ahead rather than sit around doing nothing.
I roll the save. 1. -_-
So, he basically cause the sorcerer to experience the effects of a bite, on shall we say, a sensitive area, and the guy fell prone. Which gave the rest of the party some nice bonuses to hit and let them finish him off that much quicker.