C'mon guys, this is really a thought exercise, not really a what if totalitarian disarmament scenario; in times past before themodern material age where we canbuy what knives we wish (within our respective means anyways), try choosing a favorite that you think would make you happy if you just had it. I would probably choose between the Queen Dan Burke Cattle knife and the Boker Davis Hunter II Lockback. The Queen is a slipjoint, all stainless frame parts, three blades of BG42 steel and white bone covers; the Boker is a stainless framed, single bladed lockback, S30V hollow ground blade and maroon or burgundy linen micarta covers. Probably the highest quality folders that l have. Either would work well enough. Three blades on the Queen would be better than one on the Boker, but the Boker is much more pocketable as it's much thinner and lighter. I carry and use the Boker quite a bit, the Queen not as it's so much bulkier and heavier.
Possibly one fixed could do it for me, a Russell Easler smaller drop point hunter with an ATS34 blade and stag slabs. Seven inches OAL, fairly thin and slim; it's my favorite "hunting knife" and of small enough size that few people would notice it or care if they did. No joints to fuss over and good hard rust proof steel like the two folders. I would miss a true "pocket knife", but it would work fairly well for nearly any knife chores I do.
The most practical knife that I can think of for the one knife thoughts would be one that I don't have, a Victorinox Alox Farmer. I've had and lost two Aloxes, a Pioneer Harvester and an Electrician. Both great but I really liked the sharp and handy saw of the Harvester. Another Harvester would be fine, for the second blade, which was a pruner/hawkbill type. The straight secondary blade of the Electrician was good, but I did miss the saw. Victorinox saws are the best cutting I've used out of any pocket sized saws.
Don't need to think too much about some things, it's just interesting to read what others will choose based upon what the find most practical and/or most pleasing, and these thought exercises are good to stir up a little conversation amongst us knife acquaintances and friends.