Most of the time, the RNR single rider is by far the worst. However, shortly before closing time, it's a breeze. Even though the standby line is much shorter than usual at that time, the single rider is even quicker -- a walk on, or under ten minutes. You skip the pre-show, for one thing.
I also love the Everest single rider line. It's always a short wait. As for Test Track, it's usually great. But one time, we waited maybe 35 minutes (the standby wait time was posted at 60 min. or more). I think that was our longest ever wait in single rider.
If you want to be the pilot on MF one time, it's worth getting in the standby line early in the day or near closing time. I do recommend it; the pilot seat is the most fun.