not as rare as some of the others, but much, much sadder:
in my current fort, a wave of migrants arrived. among them was Olon the thresher and Thikut, Olon's daughter. Olon owned a mule, and Thikut owned a cute kitten.
soon after arriving at the fort, Olon was struck with a fey mood. he ran to a craftsdwarf's workshop and gathered his supplies, until he demands some metal bars. I tell a rather lazy leatherworker to churn out some bars for him, but I had towait until the magma filled to full capacity for the smelters to operate. The leatherworker churned out a bar of aluminium, a bar of silver, a bar of iron and a bar of lead, but Olon still didn't accept them.
soon afterwards, Olon got angry and went beserk. the closest thing near him was his mule, and punched the poor thing in the face, killing it instantly. this got me scared that my two-dwarf milita weren't going to cut it.
next thing Olon goes for: Thikut's kitten. well, at least he finished that problem earlier than I expected.
then, Olon rushes into the farming rooms. he rushes past the five farmers in his way, and speartackles his daughter to the ground. he proceeds to mangle her until the milita arrived. he punches the first dwarf in the face, brain damaging her badly, and continued to attack his daughter.
the second milita dwarf arrived, and fared a bit better. he punched Olon's chest so hard, Olon got a fracture of his rib lodged in his heart, except that didn't bother him at all. he continued visciously bludgeoning his daughter until he bled to death.
Now i have an almost brain-dead soldier and an extremley depressed girl lying in bed with all of her limbs mangled, both kidneys with yellow wounds, and no left eye.