I only ever had a problem with one co-worker at a job years ago when i worked at a convenience store while in college, who really seemed to have it in for me for some reason. He was an older guy who refused to do anything but ride the register, which was fin by me since I preferred to stock the cooler, clean and do trashes rather than deal with customers directly.
He actually complained to the district manager saying that I wouldn't let him complete his work, when all he did was smoke constantly. No idea what his problem was. Glad he quit, but heard he died from cancer not long after. Sad, but so bizarre.