Worst jobs IMO would be sign holders. I bet time goes by so slow for them standing there on the side of traffic under the hot sun. Also, telemarketers. Calling random people and pissing them off.
Even worse yet are those that have to wear mascot costumes who hold signs as part of their jobs.
My cousin told me about this job she once had. Her dad got her the job, working for one of his longtime friends. When she got there, she asked what her duties were. The guy sat her down at this desk with a phone on it. Whenever anyone called asking where their money is, she was to tell them, "You'll get the money in two weeks." She got a billion calls a day, and told them all they would get their money in two weeks, even if they had already called two weeks ago. This was her job.
After about 3 months, she finally noticed she never actually got paid for all this phone answering. So she asked the boss about her paycheck. He told her she would get paid in two weeks.
She believed him.