OK, we all love to chat gear for no reason, so let's.
Let us say that you had to pick one prime lens only to last you forever. You cannot use a zoom ever again, and you can never change the lens. What focal length and particularly what lens would it be? For which type of shooting? Why?
Please vote and post your comments. Make sure you explain WHY you would pick that focal length and lens.
If you use full frame, just consider 50mm a Normal, 28mm a Wide and so forth... if you use medium format, well, you get the idea.
PS: if anybody votes long tele as their one and only lens, I REALLY am curious as to why.