i like all the ideas brought up so far! they are awesome poison ideas.
in fact, i have only two problems with poisons.
1)food poisoning: lots of grief potential...in fact the whole idea is grief unless you have solid intel that raiders will steal your food, and then you poison it so that they kill themselves after they kill your houses, rape your animals, and burn your villagers.
HOWEVER, the idea of poison immunities/resistances counter-balances the grief of food poisoning in my eyes. i propose immunity can only be achieved with non-lethal poisons, and lethal poisons can be resisted, but there is always a chance to kill.
2)tainted meat: the idea of tainted meat sounds good, but i don't think it should permanent. here are my additions to tainted meat.
a)perception and survival should effect your chances of detecting the taint in a food. the chance should always be small, maxing out 5-10%.
b)there should be a cleansing process for meat. you can perform it whether the meat is tainted or not. it removes any taint,
and lowers the quality, so if your over paranoid and cleanse everything, it effects the quality. or you can be super paranoid and a vegetarian, in which i will hunt you down and shove my boot so far up your ass it becomes the closes thing to a brain you have ever had.
c)the taint: when eating tainted food, it should have only a fraction of the effect of the poison used on it. lethal poison have less of a chance to kill, even if the target has no resistance. further reduction of grief!!!
well, thats all i got to say for now
"A word to the wise ain't necessary. It's the stupid ones that need the advice." -Bill Cosby