Do you have a neighbor that you just absolutely hate (if not, you can have 4 or 5 of mine) and want to fuck with?
Go to your local market and buy a bag of birdseed. The more kinds of seed in the bag, the better. Wait until the middle of the night and scatter the seed EVERYWHERE in their yard, especially in their little flower gardens alongside the house.
In just a couple of weeks they'll have some very bizarre & noxious weeds growing.
By the way, if you've got some serious White Trash neighbors, this won't work. They'll never notice new weeds.