This one is kind of an oldie, but in the original Fallout if you gave an automatic weapon to Ian (or any other companion iirc) he would more often than not shoot a spray of bullets in the general direction of the enemies with no regard if you or other companions where in front of him.
It was as infuriating as it was hilarious really. You just couldn't give him any weapon with a burst mode, he couldn't help going on a shooting spree whenever he had the chance. It was just poor AI design, but I liked to think of it as a personality trait of his. Good times.