In the end, he with the most toys wins!
I am looking at my seemingly vast array (19 in all at last count) of AI/AIS Nikkors from 16mm to 600mm and I honestly cannot imagine what other lens I could possibly need! Maybe a 200mm f/4 AIS Micro or 100mm g/2.8 AIS Micro which would give me more working distance than my 55mm f/2.8 AIS Micro but honestly I can't of anything else.
It might be nice to have an 8mm f/2.8 Circular fisheye Nikkor but for $1200 it is a very esoteric lens and I doubt I would get much use out of it. A 15 mm f/3.5 Nikkor would be neat but its angle of view is not much wider than my 18mm f/3.5