I was running the final battle in one of my major campaign arcs in a Rolemaster game. The group was fighting an evil cleric. They’d managed to take down his protectors (which weren’t easy), but had taken damage. The cleric was taking them down one and two at a time, while they had a hard time getting to him.
As things were looking bleak, in desperation, the Mage had his ferret sneak up behind and attack the cleric. He didn’t notice. The ferret attacked. Critical hit, rolled max for critical. Severed his carotid artery. As he collapsed, he attempted to heal himself, but with minuses due to a sudden frantic onslaught from the party, he failed and died.
The big bad was killed by a ferret. It was glorious.