Best Introductory Scenario(s)

Let’s keep this short and sweet: what do you think is the best introductory scenario ever written for a roleplaying game and why?

At the end of last month, I posed a similar question focused on Call of Cthulhu. This time, I’m widening the scope to include any RPG published from 1974 to the present. I already have a few favorites of my own, which I’ll be sharing in some upcoming posts, so I won’t give away my picks just yet.

What I am eager to hear are your choices, especially the reasons behind them. As I’ll explain later, it’s the why that really interests me. What makes a scenario a great introduction to a game or even the hobby as a whole? What stuck with you? What worked for your group?