Maybe not that much help on a new scenario, but I love the time to pee/go movies. I have bought everyone so far and will probably keep buying them. The amber one is maybe my all time favorite movie and I have bought several dozen over the years. Actually, I would love to see her do another if she could equal or exceed the volume from the last. The only thing I thought that could have made that one better was actually measuring the output.
Sorry, maybe not that much help, but my favorite scenarios have been the simply ones that are really just about holding as long as possible like time to go, holding contests, and capacity movies. By the way thinking about it, my second favorite all time was probably To pee or not to pee. Forgot the model's name, but I think she was offered another $100 to last another hour (it seemed not planned beforehand and really spontaneous) and she almost made it with a lot of effort and a big flood.