Practically any blue collar trade short of a pool boy.
As an A&P we do trouble shooting and repair on all sorts of systems which leads to knowledge in several fields. You may not be able to transfer and get certificates immediately but the knowledge will help in HVAC, electrical, fabrication shops, hydraulic systems (heavy equipment), small engine repair, gas turbine operations (think maritime propulsion and electrical plants).
I did non-destructive testing for a while, which is big in several industries. The aviation/ aerospace, manufacturing, gas pipeline, nuclear utilities.