Lanefan
Victoria Rules
That's not what the thread is asking though. Accidental attacks are what it's after, where the PCs never realize their target is a potential ally and-or just plain doesn't deserve to be attacked.
An example I DMed about 20-odd years ago: PC party is in the mountains and down some toughness so I decided to lob in an NPC Ranger for a while. Party had been travelling by night and sleeping by day, posting invisible sentries while at camp. So Ranger - a good upstanding sort - approaches and sees from a distance only three in-his-eyes-unguarded tents. Thinking this a bit suspicious he goes into stealth mode, and the party sentries completely fail to notice him as he sneaks up to a tent and looks inside.
In the tent is a sleeping PC, completely defenseless; so the Ranger gently wakes her up and asks a) if she's OK and b) why she is risking sleeping unguarded in such a dangerous area. The PC freaks out at a) the sight of a stranger in her tent and b) his inference that there's no guards outside. Two sentries (other PCs) hear the commotion and come racing in; the first tries to attack the Ranger and spectacularly fumbles, face-planting next to his feet. Before the Ranger can react beyond simply looking down the second PC-sentry puts a max-effect critical into his back, killing him instantly.
So yeah, it happens.
Lan-"to this day I remember the exact words I said next, through the palm covering my face: 'Nice going, guys - you just killed off your reinforcements.'"-efan
