The Hitchhiker's Guide to the Galaxy

The Hitchhiker's Guide to the Galaxy was my first experience with IF, and it was very frustrating, but in a way that entertained me greatly. The game unforgivingly kills the player again and again for oversights so ridiculous that the player was obviously not expected to even guess at them until after dying. If that's not something you enjoy, the deliciously witty prose is worth the effort, even if you resort to using a walkthrough, step by step.