Horse nettle, Solanum carolinense L., is found in open fields, disturbed ground and cultivated fields.  It has a small yellow fruit.  The leaves are spined.  Typically, spined leaves mean don't touch, don't eat.  More poisonous plants.

Christmas decoration:  dried berries (below) in wreaths. 

Medicine: Cherokee used wilted plant externally on poison ivy.  Infusion of leaves as a treatment for worms (Antihelminthic).  The leaves were said to be crushed and infused in milk (perhaps mixed with honey or sugar) and used to attract and kill flies.  

Veterinarian use: Berries were said to be fried in oil and fed to dogs, cats to treat mange.