My Favorite published adventure currently is the Red Hand of Doom. It was a great backdrop for a Mid level RPG game and it set the tone for my High level campaign after it had reached its conclusion. One of the reasons why I Really loved this Adventure was it was skilfully written in a structured sandbox style.
Once the Adventure gets going and the party learns what they are up against they are on the clock to stop it.. And the best part about the Read hand of doom for me was this was not something the players will be able to do alone. So often in an adventure the fate of the world rests in the hands of the party… Don’t get me wrong the party will play a huge roll in this adventure but the forces at work here are far beyond what a small group of adventures can handle alone. THIS single point makes the world around your players a living breathing location and it is so rare to see in a RPG game.
The Red Hand of Doom is a Dungeons & Dragons adventure designed to take characters from 6th-12th level. Confronted with the relentless advance of Azurr Kul’s horde, the characters must undertake vital missions to influence the outcome of the war. Can they shatter the armies of the enemy, or will Azarr Kul’s dreams rain destruction upon the human lands.
Personally I tweaked the written content a bit for my homebrew setting and Ran it as a 4E game. it made for a game that my players sill talk about to this day. The Battle of Brindol in the end they did not carry the day but after the street by street and door to door fighting was over. The Red Hand Had not enough forces or the willpower to hold the city. The cost was great and they players banded together with the town to save more then just its citizens that day. They may have lost the victory conditions of the scenario but the story that was told was far better then any victory. It was down right epic.
There ya have it my choice for the best Published adventure.