The Undertaker has achieved the most popularity using a gimmick that is an actual real-life profession. There probably aren't many real Undertakers who dress in a sleeveless back outfit with a purple tie when they go undertaking for the day, but the gimmick is still based on an actual career path so it counts.
Who comes in second? The Big Boss Man? Do we count Diesel as an actual truck driver? Or did he just use trucking imagery to build his character?
I'm kind of drawing a blank when I try to think of other workers who have had success using gimmicks based on an actual job. There have been plenty of failures -- repo men, teachers, baseball players, lumberjacks, ship captains, etc.