Thanks for all the replies, everyone! The most popular scenarios are the top five in descending order. Exploring the Unknown has been played and loved by 65% of responders, investigating an enemy outpost by 55%, recovering ruins by 42%, fulfilling a quest by 36%, and rescuing prisoners by 36%. Every scenario has been picked by 13% of responders, and 24% included "other". The first ten in the list are the scenarios recommended in the adventuring writing rules of the Red Box for Classic D&D, by Frank Mentzer. The latter two I added, thinking of the top of my head what others there are. Lanefan's suggestion is one big one, of course, and a few others would include fighting in an arena, leading an army into mass combat, a "reverse dungeon" where you play the monsters and try to keep out adventurers, a solo challenge written for one character of any particular class, and resurrection someone whose remains are lost or just difficult to resurrect like in the case of a fallen deity or demon lord. Perhaps "an evil adventure" should also be a separate scenario, all-inclusive.