Well the game that inspired me to post this, I had cast a ray spell, and rolled a 1, the DM ruled that it struck another PC, (not in melee with the target or in the line of fire)
This was then taken as an excuse to attack my PC, I took issue that if the DM was going to be using house rules he should have told us before the game began (I would not have taken ray spells) and everyone argued with me that fumbles have always been in the game I should have assumed.
So the striking a party member was in the rules the DM was going by, and the PCs seemed to be in favor of it but they still wanted to get mad at me when it effected them.