Weapon traps seem to be extremly efficient in this game.
I built a Labyrinth of pain that leads from my fortress to the outside and consists of lots of weapon traps with one weapon each.
Its normal purpose is to give caged goblins some kind of chance to escape into freedom (after releasing them from their cage with a lever). By choosing the right path they just be hurt by 3 whiplashes, 1 large dagger and a single stonefall trap on their way to freedom (well, none has chosen the ritght path so far) whereas every other path would have large trap weapons, 2 handed swords or crossbows as trap weapons.
Well, I found out that even traps with single weapons are extremly efficient, not only in killing my former prisoners, but also in erradicating whole suads of ambushers (who obviously find the open entrance to my labyrinth to be some kind of invitation
)
Most hostile goblins, humans and elves get killed at their 2nd weapon trap with the only exception being one single former prisoner, who succeeded in passing a whip trap, a spiked steel ball trap and finally got killed at the third trap, which contained a +large serrated green glass disc.
I was rather surprised by this, after all I had expected that, due to the fact that each trap contained only a single weapon, most prisoners and ambushers would be able to pass 3-4 traps.