Ok pitdog, after getting 3 pages of answers did you learn anthing new from these responses?
Personaly I did. One thing is the chances that you or I would have the time to only grab one knife would be not likly. If you can carry a bigger knife the chances are that you can strap or tape a smaller knife with a sheath for it or a pocket / pouch to hold a smaller knife plus some other survival gear.
Second thing is it really is neat to see what others would take for the (one knife) survival situation.
Bryan