I don't have one all-time favorite.
One of my all-time favorites is NLE: the original 17th at Hazeltine -- a 345-yard (if memory serves) par-4, with a fairly sharply uphill tee shot to a narrow saddle (upside-down saddle, that is) of a landing area, with trees on the left and trees and a creek on the right, leading to a slightly uphill approach to a rolling green, with ponds left and short right (as they remain for the current par-3 17th).
I played Hazeltine often (and not well), in those days -- in the years just before and after Tony Jacklin won the U.S. Open there ... a victory that featured a beautiful running recovery shot from the woods to the left, between the ponds, up onto the green into birdie range. (If I remember correctly, it was the 3rd round -- and he made the putt.)
What I loved about the hole (and still do love about good short par-4s, in general) is that a high-school kid with a mid-level handicap could par (or birdie!) it with well-played shots, and a PGA Tour pro could double it with an inadequate drive or approach.
I think it was PJ Boatwright who, on the USGA's behalf, told the powers at Hazeltine that if they ever wanted to host another Open, that hole had to go.