I've been playing since '79. B2 in the dining room with six-sided dice from a Yahtzee set. However, its not B2 that I remember the most. It was a borrowed module and soon returned to the owner. Then I bought S1, Tomb of Horrors. We played the hell out of that adventure. Still not the one the adventure I think of. The adventure that defined my way of thinking was X5: The Temple of Death. My friend Dwayne would runs campaigns and this would be the final adventure for my character. The reason being is most of my characters would die. I would get off the skeleton boat and get killed by the spell, Finger of Death. My characters never did saving throws well. It wasn't until my one character, Slice Handler, survived after at least of dozen of my characters died before him. There was an epic three-way battle. Slice against the monsters within and then against his own party member who had taken on the eye and hand of Venca. It came down to a handful of hit points and his last dagger that he had never used. When I think of old adventures that's the one I think of and I believe the one that shaped my gaming philosophy.
Is there an adventure that shaped your gaming style?