Yay, what a cool thread marco
My best pen & paper role playing sessions (had many of them
) was with a Call of Cthulhu adventure called 'Bruderschaft des Tieres' (Brotherhood of the animal). I don't know if there is a english version.
I was the 'dungeon master' and had four players. The adventure was a campaign consisting of about 7-8 chapters that lead to the grand final confrontation the 'the animal'
The plot was just great. Each chapter revealed more of the conspiracy of the brotherhood and it drew the players in a dark sinister world. The players really were playing their roles and solved the puzzles with a very few hints. Like in every good Call of Cthulhu session one of them went insane
The final 'battle' could only be won by offering a huge amount of mana to ban the animal in a ritual. I added a kind of epilogue to it in which I described how the broken heroes tried to return to their normal lives, but that they couldn't forget the events.
It took about 10 quite long sessions to play through it and I can't remember another adventure where the atmosphere grew so intense. Okay that was my best retro roleplaying expierence