Doris,
Sam mentions a couple of nice knives. I own and use both the Mora and the Swiss Army Classic under different circumstances. Noting that you only want this to make wood shavings in "emergency" situations I would suggest the Swiss Army Classic.
At one ounce the Classic can whittle down to dry wood. It will be a bit of a chore because blade is small, lacks heft does not take or keep a fine edge very well. But it will do in a pinch. It will also cut your toenails, pull a tick, strike a match and file a nail. Just keep it as sharp as you can.
The Mora may be the finest blade available for under $20. (In fact, I think I bought mine from Sam). I would put it at somewhere around 5 oz, not particularly small or light. Mine is used on longer or wetter outings when I can expect to need to split branches to get to the the dry stuff. I need to feed a BushBuddy. It readily takes and holds a good edge. Great for frequent use, overkill for emergency use.
I don't like razor blades when put to wood. They snap easily when twisted and for anything more strenuous than cutting paper, foil or tape I think they can be a little hazardous. For some fraction of an ounces you're better off with the more versatile Classic, imho.
Hope this helps. I have loved knives ever since I was 7 and won one at a local fair. Parents made me exchange it. If I could justify any reason for carrying one or paying for one I would own a Busse Battle Mistress:
http://homepage.mac.com/zombiekiller/badmojo/bm.html
But then I'd have to disappear into the Canadian interior before missus skinned me with it.
Paul