Very simple minefield is TheFlame52's embark-surrounding cage trap circle.
If you used appropriately-staggered floodgates, you could use that as possible werebeast trap (it takes a while to destroy one, so this would run down the timer - perhaps cage-trapping them if you also have the trap circle, not sure. )
Hm, for a mine-like option, you could have hatches with ramp-bouncing minecart below - when a creature takes a "shortcut", they'll get minecart to the face.
@Grim Portnet: You could include an auto-disable by having the pump be powered by magma-unsafe mechanism from the front of the pump.
Or a magma-sensitive pressure plate that latch-closes pump intake, I suppose
I remember a thread where someone had done the magma landmine thing with instant, zero lever action. You could manually trigger them yourself without waiting for a lever pull. I forget how they worked though. Can't tell from the video if this is using that idea.
When a built and raised raising bridge is marked and unmarked for deconstruction, it will let take on a statue-like state, thus letting fluids through from NSWE and above until it is lowered and raised again.
So you'd use a setup like
_>____▒
~%%▒╬
~~~~~▒▒
~Optionally, adding a pressure plate into tunnel or over downstairs above the bridge (by building floor over dug downstairs, then deconstructing) to reset the bridge and perhaps also to trigger when enemy steps on them.
Technically, can do this with ice too, but resetting is much more of a hassle with it.