All right. This is a weird thing. The short version is that I seem to have gotten kinda punked by a goblin ninja.
Long version:
Setup: I always have at least one and up to four execution rooms in my fortresses. In my new, 5-year-old 0.34.10 fortress, I have two. The first one is a firing range with two platforms separated by a retractable bridge; hostile cages go on one side, marksdwarves on the other. The other one is a shallow 4-z-level pit with wooden spikes; I chuck the goblin down, and have soldiers-in-training waiting below to trash the stunned and wounded goblin that's been thrown down the pit.
So the second great big goblin siege hit in Autumn 255, elite goblins, war jabberers (as mounts and otherwise), the goblin general, the whole thing. They are repelled without casualties except for the dwarven caravan, which is wiped out. Cue two months of cleanup. It turns out I've bagged one of the goblins in one of my wilderness cage traps. A goblin bowman. Okay, so I want to use the second execution method, can't very well have the target shooting back at me can I? I send a couple training squads of hammerdwarves to wait at the bottom of the pit.
I tune in again just in time to see a dwarf throwing an oddly cyan bowgoblin down the pit. When he hits the spikes, I see that he is in fact Goblin Swordmaster Stozu Etospukge!
Goblin Swordmaster Stozu takes a wooden spike to the lung and to the kidney, but gets right back up and starts parrying the mostly Competent hammerdwarves effortlessly. I check the logs and realize that while he is a swordmaster, he is equipped with a bow for some reason. I stop panicking. Then, one of my hammerdwarves goes down. It's an iron bow, so it's enough to brain a dwarf with.
I order the proper infantry, expert swordsdwarves with steel swords, to deal with the threat. There's a couple of traps in the hallway to the pit but not enough to stop a master swordsgoblin, and soon, he'll be smack in the middle of my hospital if I'm not careful.
The goblin manages to put arrows in two of the other hammerdwarves. They writhe around uselessly. The goblin ninja has holes in his lung and kidney; these two dwarves just have arrows in their arms. Great. The third one was unhappy when he marched down there in the first place, and is unhappy now. The proper infantry is still mustering down the central ramp.
The goblin ninja and the dwarf fence around for another twenty moves or so. What will end this? Of course: by deploying the classic dwarven cheek bite, the last hammerdwarf finally gets the upper hand over the ninja, gets a painful enough shot in to drop him to his knees, and proceeds to bash his head in. I have prevailed!
But what the hell? He really did show up on the units screen as a regular old goblin bowman.