My interpretation of your question starts with courses I find to be on the extreme of the "difficult" spectrum. I think of the following:
Bethpage Black
Winged Foot West
Spyglass Hill
PGA West (Stadium)
Pine Valley
Each of these courses is how I define "difficult" due to a few factors.
1) During play and upon immediate reflection of the round, I'm made brutally aware that golf is very hard and I do not posess an array of shots nor the ability to call on them when needed (I play off a 6 handicap and believe I'm the definition of Snead's line, "you have to dance with the girl you brought". If I'm drawing the ball on the range, I have to sling it around the golf course. If I see a fade that day, I'll slice it around the course. Once I get into that groove, I'll throw a double cross into the situation really fast)
2) While I love golf and can play till the sun goes down when granted the appropriate hall pass (rare these days), each of the above courses represent ones in which I finish 18 and say, "thank god the clubs are going in my trunk".
Of those I think the only one I would say I would take every day over any other course would be Winged Foot West. In my opinion, when playing from the proper tees-I think it becomes slightly more playable, but only when the rough is manageable.
I would much rather take the hypothetical/fantasty golf question of "what fun course would you want to play every day" and names like Newport, CC of Fairfield, Shennocosset, Cypress Point, etc. come to mind.
Great question and I'm interested to hear others feelings on truly difficult courses.
Mike