I was greatly amused by the monkey torture earlier in the thread.
Anyway, I've had many cases of missing and mangled limbs, horror stories created by my modding in genitals for all creatures (truly I am evil for enjoying this), etc. But two have really stood out.
The first, being the worst but not chronologically first, a soldier-class I can't remember, but melee-was sent to guard the underground river in one 40d16 fort where I hadn't set up a well or finished the water management systems, the ponds were perpetually empty, and I frequently ran out of booze (managing the barrel-to-edible-goods ratio can be difficult in arid, treeless environments) I was watching at the time designating the tunnels where the water channel would soon be dug, and saw him/her fall into the river, chasing/dragged by some of the various residents. They were dragged downstream, over a waterfall, at the bottom of which he fought for several real-time minutes (a week or so?) before bleeding to death, I couldn't have saved them with the animal-men even though they lived long enough for me to have gotten a miner up there to give them a path, a shame really. I checked their wounds, inventory, all their personal info during the fight. They managed to kill several of the beasts, including a crocodile, two olm-men and two frog-women, and suffered red and yellow injuries to every part of the body, and several things lost. Miserable by the time they died.
The second that has stood out, is a marksdwarf who suffered an eye injury from god only remembers what (but probably the orcs...). Not particularly horrific, barely a setback. Except that he would randomly fall unconscious every couple minutes, not every time he took a step, not every other step, he could perform a few tasks in the meantime. I decided to watch him more closely at one point, checking his wounds page constantly. Nothing. The eye was missing all right, but he was NEVER in pain, never exhausted, stunned, winded, anything, and had no other injuries. It was a bug, probably.
Eventually he passed out during a very fateful battle (and stupid on my part) and miraculously survived unharmed after all the others had been incapacitated or killed, and began sniping the orcs from his position across the river. By that point they'd run out of ammo (how miserable a force we are to have to wait for them to empty their quivers! of course they're idiots too for not leaving afterward.) and I was solely interested in cleaning them up, so he wasn't being particularly heroic. We only lost a couple civies and a couple less productive marksmen (my only military in that fort since I was walled in and had bridges to retract across non-freezing rivers)