1. Round Up - an herbicide that the previous owner of this house used with abandon and killed all sorts of wonderful things... It's been 10 years and it's still devastating. The house was originally owned by someone in the botany department at UGA.
2. Poison Ivy - a weedy indigenous perennial plant that has oils in the leaves which when in contact with human skin results in really bad itchy rashes that break out in little clusters of boils which spread when scratched.
Of the two, and while it pains me to admit it, I dislike being incapacitated by poison ivy rashes which I have a REALLY BAD allergic reaction to... the poison ivy growing near my office got it.