You're not serious, right?
Really, we *need* air, shelter, water, fire, and food. (Clothing falls under the shelter category!) But in order to produce some of those things in certain surroundings, a knife (or knives - as the case may be) consitutes another 'necessity'.
To answer your question, IMHO, I would *need* three fixed blades (one large - around 9" to 12" blade; one medium - around 5" to 6" blade; one small - around 2 1/2" to 3 1/2" blade), and a Swiss Tool. However, three folders would be near-needs: My Military (mainly for food prep), my Wegner (mainly for skinning and other 'dirtier' chores), and my Calypso Jr. Ltwt. (for my few 'Sunday-go-to-meetin'' excursions where I may encounter many of that dreaded species: 'sheeple'
). Of course I'd also *need* some sharpening stones, a few gallons of Marine Tuf-glide, a few gallons of mineral spirits, to keep he wares in good working order.
And, given a *need* scenario, I'd also need a good woman to keep me company (I've got the best already!), and a fast computer with internet connection to keep in touch with y'all and all these great topics!
Gotta love it!!!
------------------
Champions make improvements as fast as losers make excuses.