CAD / CAM & Machining.
Co-bots help tremendously at the present, and once a job is 'running' it's very automateable, but getting a job to that point of automation takes tremendous human skill and efforts. Machining touches every physical thing around you. There exists huge potential for more machine learning and automation with coming generations of robotics and edge computation, yet we are a long ways from generalized robots and embodied "AI" that are be able to conceive a new part or whole machine from its parts and make it out of mill stock.
LLMs alone will never accomplish that frontier.