There are a number we like, as a matter of fact, we purposely don't book FPs for some rides just because we love the line. Our favorites:
Jungle Cruise, the first part of the line is a bit boring but once you get inside the announcements are funny.
Big Thunder Mountain - again the outside part is boring but once you get to the outer edges there are lot of things to play with. We like to prime the dynomite pump and watch it explode out the window.
Haunted Mansion - reading the headstones is a hoot.
ToT- we love just looking around the grounds and, of course, once you get inside the lobby is great.
GMR - we love looking at all the costumes in the lobby and watching the movie. Last trip we actually asked if we could step out of line and watch the whole thing then get back in the back of the line at the back of theater. The CMs were great and actually just let us get in line at the door when we were done.
EE - sadly we tend to do single rider now and miss that line.