My biggest pet peeve is management trying to take away an operators ability to think and do their job. Stupid alarms or lockouts or stripping down functionality because they are afraid their operators aren't competent enough to run the machine. In my experience give the operator as many tools as possible and they will make the machine run better than any amount of situational code.
Still...Id rather limit finite control of what an operator can do, then have an inattentive operator melt down or destroy a $1.5M heat exchanger.
My biggest complaint is as Tom Jenkins posted: Being requested to modify code to try and make a poorly engineered process run.