My badger pit(s). I've been improving on the design with every fort. As it stands, the thing sort of looks like this:
O=wall :=open space D=door F=floor B=bridge T=weapon trap, each containing 10 spiked wooden balls
O O O O O O O O O O O B B B O O O O O O O O O O O
O : T : O
O : T : O
O : T : O
O : T : O
O : T : O
O : T : O
O : T : O
O : T : O
O : T : O
O : T : O
O O O O O O O O O O
O : : : : : : : : O
O : : : : : : : : O
O : : : : : : O O O O O
O : : : : : : O B D F F <--- leads to badger storage, can dump badgers in through here.
O : : : : : : O O O O O
O : : : : : : : : O
O : : : : : : : : O
O : : : : : : : : O
O O O O O O O O O O
O O O O O O O O O O
O F F F F F F F F O
O F F F F F F F F O
O F F F F F F F F O
O F F F F F F F F O
O F F F F F F F F O
O F F F F F F F F O
O F F F F F F F F O
O F F F F F F F F O
O O O O O O O O O O
There we go. So anyway, I still need to test if dwarves freak out when there's a mass of gobbos and assorted wildlife two z-levels below them, but the plan is that they dodge into the pit, where they have nothing to look forward to except the occasional badger, giant badger, badgerman, or war-version of any of the three to drop in for a visit. It hasn't gone wrong yet, and for added fun I enjoy lining the walls up top with cage traps to discourage nasty little theives.