Had on one of my early flights as an FO in 737 an autopilot failure. That night I had to fly manually all the way from EDDF to LGTS above FL 300... My captain let me fly all the way, because he said, it would be a good training...
Not enough we had to enter a holding (I believe it was at 9.0 DME at MKR) and do a VOR approach. The flight took about 3 hours - I was afterwards really trashed - and the passengers probably as well....