Great question! The Circle Waltz that Alan mentions is my all-time favorite as well, but I know it by the name of "Oslo Waltz Mixer." I like it because, along with the reasons Alan gave, it's complex enough for experienced dancers to really enjoy it while being simple enough for beginners to succeed if it's taught well. For ONS, I also like La Escoba (the Broom Dance), which has a funny show-off component as well as long waltzing portions. (Line up facing P. Begin w/ one extra gent, who waltzes/cavorts with the broom between the lines while everyone watches. Suddenly he drops the broom & grabs a partner. Everyone rushes for a P, all waltz. When phrase ends, line up again w/ new man out dancing w/ broom.) I wamt to try Valse Cadena (the Chain Waltz mixer) soon. Anyone had experience with it? Tina Alan Winston said, <<"Circle Waltz" (Big circle, balance and roll-away 4x, with this one balance in and out, roll in, repeat going out, chassee in, chassee out, waltz around) or some variation, because it's so accessible, connects the whole room repeatedly, lets you see most of the opposite-sex people in the room if only for a fleeting moment, and works with many flavors of waltz.)>>