Echo the "vintage" road bike. We got our teenage son one during one of his huge growth spurt years. Cost was small, put on new tires and brake pads, swapped the saddle. It was a catchy red color, really caught his eye - took about half an hour for him to get comfortable with the down tube shifters. He rode it around 1200 km during one season, including a 500 km trip with us. I think he was suprised how nice the steel frame rode and seemed sad when he outgrew it. Got more at a bike swap than we paid for it.