I once got to ride Test Track three times in a row, all alone. There was nobody else on the ride. It was such a weird to experience to see this attraction that is usually so full of people without another soul on board. It had poured until about 10:00, so the park was empty and Test Track had just reopened (I was quite surprised they actually bothered so late at night and with the park so empty). I got some great shots of World Showcase without anybody else. I would have been able to get a few more rides in but it started raining again on my third cycle. Just a note, Test Track is not fun in the rain.
A couple times I have purposely ended up in the corner of Frontierland that contains Splash Mountain and Big Thunder Mountain Railroad during SpectroMagic. On both I have had Cast Members offer to let me just cycle through so that I could watch Wishes.
Another night I got stuck in Adventureland during SpectroMagic. I ended up taking a few cruises on the World Famous Jungle Cruise when the skippers realized I was repeating the attraction (I had actually jumped on to pirates in between a couple of my cruises, but the land was very empty). They started asking me what I was up to and eventually I was just hanging out at the loading dock and getting on different cruises so that I could experience each skipper's version of the attraction. I ended up taking twelve cruises that night.
The Animation Academy at the Studios is open and little visited during Extra Magic Hours. One day I had decided to do all of the shows (except Playhouse Disney) and little things that I had skipped on previous visits. I wandered into the Animation building and then the Animation Academy. It must have been awhile since the classes had been somewhat well attended (about half full) as the Cast Member teaching us invited everybody to just sit and stay. A few of us ended up just spending our Extra Magic Hours in their learning to draw various characters and talking with the Cast Members in between classes.