My first thought was that I rarely use published adventures anymore, but then I realized I did at least read the bajeezus out of them when I was a more fledgling GM. And there was one that blew my teenage mind....
For those who don't know, the Assassin's Knot is a low-level murder mystery, the sequel to L1: the Secret of Bone Hill. An NPC from L1 is killed, and three clues lead to three different residents of the village where the module takes place. The PC's have to go into the town and instead of just killing everything in sight, interact with all the villagers to see who might have done it. There's a few hooks for action here and there for the players who need it, but the bottom line was this was the first module where the GM had to really think about what a fairly large number of NPC's would be doing in response to the players' actions.
Plus I was, and still am, a huge fan of murder mysteries, especially the "English manor" style mysteries of Christie and Marsh, and this module reeks of it.
Final note: it also features a table for which random NPC is using the privy at any given time, in case the PC's want to stake that out. Awesome.