Since I mentioned this book in another thread (and it remains one of my favorites) the first line of
Running with the Demon by Terry Brooks:
He stands alone in the center of another of America's burned-out towns, but he has been to this one before.
Like many have stated about other openings, this opening lines both sets the stage and raised questions. Since we're in "another of America's burned out towns" we know the scene is post-apocalyptic, but we wonder why. What destroyed America's towns? And, of course, we're told "he has been to this one before". Why? What was he doing there, and why did he come back now? I'm interested.
Another of my favorite openings ever is from the (sadly, no longer in print) Young Legionary series by Douglas Hill. The "cold open" of
Galactic Warlord remains one of my all-time favorites, but even the first line also does a lot to draw you in.
He had been walking the dirty streets since twilight first began to gather. The pain streamed like liquid fire through every cell of his body - but he locked it away in a corner of his mind, ignored it, and walked.
"Dirty streets at twilight" is a very evocative visual, even if we don't know this is a sci-fi book (it has a spaceship and explosions on the cover, of course). Then, of course, we know our protagonist is in horrific pain, yet somehow has the will to fight it off and compartmentalize it. So we know we're dealing with a very tough individual. So I want to know where this person is going, why they are in horrific pain, and how they are tough enough to ignore it. The rest of the opening, of course, just gets more interesting from there.