A knife. Any size, fixed or folder. With a knife I can make or rig virtually everything else. Without a knife, I would have to try and find a rock to make sharp.

Compass, eh. I can figure directions close enuf for traveling. Lighter, probably, but there are alternate methods. Flashlight - unless it was that tunnel or building - something I can live without.

And my wife wonder why we have so many knives in so many places.