Around home I use a light a lot more, and can always get a knife from the kitchen drawer if I need one. Outdoors, probably knife, though it seems like a false dilemma. You want a knife of reasonable size, but even a tiny keychain light (I mean the coin cell Photon style, not a high power one) makes a ton of difference. And a small modern 1aaa light is almost as good as a big light. Add a little bit of elastic cord and you have an impromptu headlamp.