Since so many traditional ideas didn't seem to fit your bill, I tried to "think outside the box". These are some some pretty wild ideas, don't know how helpful any might actually might be:
Is it legal to put a silencer on a gun where you live?
A crossbow is more easily aimed than a standard bow as you don't have to hold the tension while aiming.
BB guns can shoot .177 steel darts. I know this seems bizarre, but I wonder if you could take a high velocity pump action BB rifle, modify a dart with concentrated poison and shoot it with that. Or what about those tranquilizer guns they use to tranquilize bears, etc. Put the thing to sleep, then lay it in a homemade guillotine and dispatch it quickly and painlessly! (I can see my new 3ph attachment now: it uses the PTO to winch up a 500 lb. blade, 10' into the air!! Then, SWOOSH!!!!!

)
I also like the idea of a good hunting dog. What about a coon dog? Though most people think of them as harmless weiner pets, Daschshunds were bred to dig into the ground and kill ferrets & weasels. As a kid, I had one that went after Hispid Cotton Rats like crazy. It was so agressive it jumped a neighbor's German Shepherd four times. As soon as it got its 60-80 stitches out, it went straight after the G.S. again. Dad finally gave it away and told me it'd died at the Vet's office

. One of my neighbors today has some little furry dog I'd never seen in North America that was bred in Europe to ferret out and kill rodents. It's smaller than a beagle, but all it ever has on its mind is sniffing out something living to bite and rip apart.
On a different topic running in this thread, I know everybody calls them the Ozark Mountains, but every map I look at indicates that the Ouichata and Boston Mountains are situated on the Ozark Plateau. Anyone who lives there ever hear the topography referred to in those terms? Guess it's kinda' like south GA where I grew up, a large mouth bass is usually called a trout. Most've my kin folks there are like those hillbillies: they've never traveled far enough to see a trout

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