My husband is a chef, paid hourly, and he just found out they have been basing his pay on his scheduled hours not his actual hours- a lot of times he gets in and his boss asks him to clock in early or they have to stay late to close. I know he should have been tracking his actual hours to paid hours all along, but he's too trusting for his own good.
Additionally, I know a company that intentionally schedules hourly employees for less than 40 hours and usually makes them work some non round number of hours like 37.25 or something. Then pays them for less like 35.75 hours. Most of the time, the employee fails figure out their correct gross pay due to their lack of math skills. If the employee catches the "mistake", the company pays them immediately and claims a clerical error.