Worst: Third shift manufacturing gig I got one summer. We were wrapping and taping transformers. An entire summer of my life *poof* gone. I never learned to sleep on that schedule. I even hit a deer coming home from that job and ended up walking the rest of the way.
Best: Bike shop in college. Learned some wrenching, hung out with mtn bikers, got my parts cheap, made some long term buds.