Hmm... another challenging post. Given the many games I've run, if I were to stick to White Wolf, it would be the Changeling multi-chronicle game I had (It spanned three generations of characters). Some would feel the best adventure I ever ran would be Sacrament, that had four players, and around 13 Lurkers who were non-players but were given information on the game's plot and the freedom to contact the players "in character" whenever they wanted to. It was a meta-fest that really hit awesome moments. ("Tobie, can I help the players in the scene? One is texting me to help out." Me: "Sure, we're playing at [name of venue]. If you can get here in thirty minutes, you're in the game.")
But again, I have to keep the answer Vampire-centric to match the 30-Day challenge theme, so with that in mind, I think I would have to choose:
We just can't get enough of this adventure. Yes, lots of naysayers out there will cite how rail-roady it is, with unbalanced characters and insane scenes, but in many ways those are the things that make us love it. The rail-road allows us to explore other avenues without leaving the plot. The unbalanced characters tells us to stop thinking about "defeating them" and instead allows us to explore interacting with them in various ways. It is like enjoying a movie you've seen over and over again. There's always some new angle to discover. Some new scene to appreciate. Some new line to throw.
And yes, we do twist things around. I've had games were Marianna DIES during the Last Supper, and all Marianna scenes later on are attributed to the actions of a player. I've had a version were all save for three Conspirators were destroyed by the Founders. This lead to the Conspiracy of Isaac being more ruthless and cruel in their later actions. I've even had a game where one player ends up the Childe of Ambrogino Giovanni. Oh yes. That child would, in the end of that game, diablerize his very own Sire in a bid to claim the Tetragrammaton for himself.
Giovanni Chronicles are such a delight to run.